How Do You Inspect Protective Cases on Arrival? A Batch Incoming Inspection Workflow

The short answer: incoming inspection of a protective case shipment is a fixed workflow of four gates plus one table. The four gates are document and marking verification, appearance and dimensional sampling, functional sampling, and a quick seal check. The one table is the sampling plan read from GB/T 2828.1 (identical to ISO 2859-1) or ANSI/ASQ Z1.4, which walks from lot size to code letter to sample size and accept/reject numbers. Programs that fail are rarely failing because nobody sampled. They fail because three things were left undefined: how the inspection lot is formed, what the acceptance basis is for each gate, and which disposition path a rejected lot follows. Leave any one of those open and the receiving dock stops judging against a standard and starts arguing from experience.

This guide is written for buyers, warehouse supervisors and quality staff. It gives a workflow you can paste into an incoming inspection work instruction. It covers what to prepare before the truck arrives; the items, tools and thresholds for each of the four gates; how to read a sample size from lot size and inspection level; whether separate shipments can be merged into one lot; the fields of an inspection record; four disposition paths for rejected lots; and how inspection intensity should scale with shipment size. All figures are marked as typical or empirical values. The binding text is always the technical agreement, the signed golden sample and the current revision of the named standard.

Contents

• The short answer: four gates and one table
• Preparation: translating the agreement into an inspection card
• Gate one: documents and markings
• Gate two: appearance and dimensional sampling
• Gate three: functional sampling of latches, hinges and handles
• Gate four: quick seal check and ingress protection confirmation
• Setting the sampling plan: lot size, code letter and acceptance numbers
• How to form an inspection lot: can shipments be merged
• Inspection records and disposition of nonconforming lots
• Judgement calls on the dock and recurring disputes
• Linking incoming data to the supplier quality record
• Inspection intensity by shipment size
• Frequently Asked Questions
• Conclusion and Related Reading

The short answer: four gates and one table

Start with the skeleton. Incoming inspection of a protective case shipment is a sequence of judgements, not a random grab of a few units.

The order cannot be shuffled. Documents first, because otherwise you sample for an hour and then discover it is a different order. Appearance and dimensions next, because a case that fails the visual basis has no business proceeding to a functional test. Function before seal, because a latch that does not fully engage will itself cause a seal failure, and testing seal first invites misreading a functional problem as a gasket problem. If the order holds, the judgement holds.

The one table means the sampling plan, not the phrase "AQL 2.5." A complete sampling plan statement contains five elements: standard and revision, inspection level, sampling type (single, double or multiple), defect grade, and the AQL with its accept and reject numbers for that grade. Drop any one and the same number resolves differently in different tables, which is exactly how a standoff starts at the dock.

One premise that is easily forgotten: sampling is accountable to the lot, not to the unit. Passing inspection means the lot is statistically acceptable. It does not mean the unit in your hand is good. So any characteristic that is safety related or carries severe consequences, such as latch retention, handle strength or leakage at the declared IP rating, should not rest on sampling alone. Put those on zero acceptance or full inspection.

Preparation: translating the agreement into an inspection card

Most disputes are born before the truck arrives, inside a technical agreement that says "appearance shall be good and the product shall conform to drawing." An inspector cannot judge against that sentence.

Step one: translate each requirement into action, tool and threshold. Three examples.

1. "Sealing shall be good" becomes "Establish minus 20 kPa gauge pressure in the dedicated fixture, hold for 60 seconds, and accept if pressure decay does not exceed 2 kPa."
2. "The handle shall be secure" becomes "Load to the rated 25 kg, suspend statically for 10 minutes, and accept if there is no whitening, cracking or permanent deformation at the handle root and its mounting boss."
3. "Dimensions shall conform to drawing" becomes "Judge the three key external dimensions against a tolerance of plus or minus 1.0 mm, and judge gasket land flatness at 0.5 mm."

Step two: prepare three physical references. One approved golden sample, one boundary sample, and one set of critical component samples covering the gasket, the latch and the hinge pin. All three must be signed by both parties, labelled with a number and a date, and stored out of direct light. Without a golden sample, appearance judgement reduces to whoever speaks loudest.

Step three: attach the sampling table itself. Do not write "AQL 1.0" in the body of the agreement and stop there. Print the GB/T 2828.1 or ANSI/ASQ Z1.4 table covering at least the lot sizes your program can produce, attach it behind the inspection card, and let the inspector read rather than interpolate.

Step four: prepare and calibrate the tool list. A typical set looks like this.

Calibration deserves emphasis. Measuring handle strength with an uncalibrated force gauge is the same as not measuring it. When supplier and buyer use tools of different accuracy on the same lot, the disagreement usually comes from the tool, not the product. Writing "judgement rests with the buyer's calibrated fixture" into the agreement removes a large class of arguments.

Step five: define the inspection environment. Visual inspection is best performed under 800 to 1200 lux with no direct glare, at a viewing distance of 300 to 500 mm, for 10 to 15 seconds per unit, from a normal use angle. Putting those conditions in the inspection card prevents the inspection from drifting into an unlimited search for blemishes.

Gate one: documents and markings

This gate samples nothing. It compares the whole shipment against the order, with one purpose: confirming that what arrived is what was bought.

Document checklist, selected by order type:

1. Packing list and commercial invoice, checked for model, quantity, colour and pack quantity.
2. Factory inspection report or certificate of conformity, checked for a matching lot number, inspection date and verdict.
3. Material declaration or resin grade statement, confirming the resin and gasket material match the agreement.
4. Any special test documents required by the order, such as IP verification reports or flame retardancy declarations.
5. For export orders, the compliance declarations required by the destination market.

Marking checklist:

• Carton label: product name, model, quantity, gross and net weight, carton dimensions, country of origin, lot number.
• Product marking: model, lot number (including cavity number where the mould carries one) and date of manufacture.
• Packing method: consistent with the agreement on single or multi-unit packs, liner inclusion and instruction sheet inclusion.
• Pallet and wrapping: consistent with the agreed stacking layers and stretch-wrap requirement.

The three most common failures at this gate:

Incomplete documents are not a quality failure, but they are a risk signal. A stable supplier produces factory inspection records on request. Repeated "the report will follow next week" usually means process control is thin. That signal belongs in the supplier scorecard, not in an argument won at the dock.

Gate two: appearance and dimensional sampling

Appearance and dimensions are the most frequently performed gate and the easiest to turn into a formality.

The appearance basis must be graded by location. The same sink mark is a major defect on the gasket land and a minor defect on a non-structural cosmetic face. Read the case in three zones: the sealing surface and gasket land, which is strictest; structural and load-bearing areas, which is next; and cosmetic faces, which is most forgiving.

Typical appearance defect list:

• Sink marks, weld lines and flow lines, especially on the gasket land, reinforcing ribs and hinge bosses.
• Flash, examined closely at latch engagement faces and the parting line around the gasket land.
• Colour deviation and colour streaking, compared against the golden sample.
• Scratches, scuffs and gouges, with a clear distinction between as-built damage and transit damage.
• Interior scratches, ejector pin marks and stress whitening around metal inserts.
• Liner defects: poor bonding, adhesive failure, bubbles, rough cut edges.

Attributing scratches is the most common dock dispute. Three tests help. Check whether the packing material carries matching abrasion marks, since transit damage usually leaves a regular friction pattern. Check whether the position clusters on stacking contact faces or pallet edges. Check whether several units in the lot show the same mark. Agreeing illustrated criteria for as-built versus transit scratches in the inspection card removes most of the argument.

Do not measure everything. Measure the right things. Three families matter: assembly-critical dimensions such as cavity length, width and height and mounting hole positions; stacking-relevant external dimensions; and seal-relevant mating dimensions such as gasket land flatness and gasket groove depth and width. Everything else is confirmed at first article and not re-measured every lot.

Example dimensional judgement structure:

Appearance and dimensions normally carry separate AQLs. A common arrangement is AQL 1.0 for major and AQL 2.5 or 4.0 for minor. Note that minor appearance defects must always be judged under the stated viewing conditions, otherwise a single case can yield blemishes indefinitely.

Gate three: functional sampling of latches, hinges and handles

Function is where the value of a protective case actually lives. A case that passes appearance but whose latch is half engaged will open itself in transit.

Latch check. Operate each sampled latch three times by hand and confirm a definite engagement feel, either audible or tactile. Confirm that the latch does not release when the loaded case is tapped on the side. Confirm that left and right latches require comparable force. Confirm that no sharp edge or burr sits on the latch paddle. For padlockable versions, confirm that the shackle passes through and locks properly.

Hinge check. Movement should be smooth with no binding or abnormal noise. The lid should hold at the fully open position where the design provides a detent. When closed, the gap between lid and body should be uniform with no visible offset. Where the hinge pin is metal, check for axial play.

Handle check. Two conditions matter: static suspension and dynamic shock. For static suspension, load to 1.5 to 2 times the rated load as an empirical guide, hold for 10 minutes, and inspect the handle root, mounting boss and body interface for whitening, cracking or permanent deformation. Dynamic verification by drop and vibration follows ISTA or the relevant GB/T 4857 methods and belongs to type testing, not to every lot.

Recommended functional sampling scheme:

The most common deviation here is testing a single unit. Functional scatter is usually wider than appearance scatter because it depends on assembly tolerance, component lot and operator technique. A reasonable rule is that the functional sample should be at least one third of the appearance sample, and never fewer than three units at small lot sizes. For safety-related characteristics, treat them as critical and apply zero acceptance.

Gate four: quick seal check and ingress protection confirmation

Sealing is the defining characteristic of a protective case and the easiest to misjudge visually.

The recommended routine quick check is pressure decay under negative pressure. Build a dedicated fixture, establish a defined negative pressure inside the case through a vent or a dedicated port, typically minus 20 kPa, hold for the specified time, and measure the decay or convert it to a leak rate. Accept if the decay stays within the agreed value. The method is fast, non-destructive, suitable for covering a large sampling fraction or even full inspection, and it indirectly reflects gasket compression and gasket land flatness.

Where the case carries a pressure equalisation valve, switch to positive pressure. That merges valve function verification and seal verification into a single operation, which is more efficient. Note that the valve's cracking pressure and its closed-state sealing must be confirmed separately, otherwise a case can pass the body seal test while the valve leaks slowly.

Three points on setting the threshold:

1. Match the negative pressure and hold time to internal volume. Larger volumes produce smaller decay for the same leak, so a large case needs either a longer hold or a leak rate criterion.
2. Equalise ambient temperature first. Temperature change moves internal pressure and can mask a real leak, so let the case stabilise for about 10 minutes before testing.
3. Allow for the fixture's own leak floor. Measure decay with the fixture empty, without a case, and subtract that baseline from the result.

Final confirmation of the IP rating belongs to type testing, not to routine lot inspection. Verify the declared rating using the immersion or jet methods defined in IEC 60529 or GB/T 4208 at design freeze, after material or mould changes, after a long production pause, or when the customer specifically requires it. Writing a full IP test into every lot only pushes suppliers into box-ticking or into walking away from the order. For the verification approach and the documentation to request, see how to verify IP67 certification and test reports.

Common root causes of seal failure, in the order worth checking:

Setting the sampling plan: lot size, code letter and acceptance numbers

The sequence is fixed and cannot be reordered.

Step one: read the code letter from lot size. Form the inspection lot first, as discussed in the next section, then choose the inspection level. General level II is the default. Level I reduces the sample and suits high inspection cost or a stable process. Level III discriminates better and suits high-risk products or safety-related characteristics. Special levels S-1 through S-4 are reserved for destructive tests.

Step two: read the sample size and acceptance numbers from the code letter and the AQL. Take general level II with a lot of 1201 to 3200, which gives code letter K and a sample of 125. Reading the AQL 1.0 column gives an acceptance number of 3 and a rejection number of 4: draw 125 units, accept at 3 or fewer nonconforming, reject at 4.

Step three: judge each defect grade separately. Critical defects run at zero acceptance, while major and minor have their own columns and their own verdicts. The three do not offset one another. A major defect rejection is not excused by a clean minor result, and vice versa.

Quick reference for common lot sizes, general level II, single sampling, normal inspection, shown as accept/reject:

Three cautions when using this table. First, where an arrow appears, meaning the cell is not a standalone plan but points to a plan above or below, follow the arrow to the sample size indicated and never interpolate. Second, the same lot size yields a different code letter and a very different sample size at a different inspection level, so the agreement must state the inspection level explicitly. Third, destructive samples do not count toward lot acceptance and must be drawn in addition.

AQL is not a permitted defect rate. Its meaning is that when a lot's true nonconforming proportion equals that AQL, the plan accepts the lot with a high designed probability. Two risks therefore exist near the AQL: a good lot may be rejected and a poor lot may be accepted. The right way to reduce risk is not to lower the AQL number but to improve process capability, sharpen the test items, and agree switching rules for tightened and reduced inspection. For a fuller treatment of defect classification and sampling design, see acceptance criteria for custom protective cases: AQL sampling and factory inspection.

How to form an inspection lot: can shipments be merged

How lots are formed directly determines sampling volume. Split finely and inspection volume grows. Split coarsely and risk concentrates.

Three principles:

1. Prefer one production lot per inspection lot. Product made on the same day, on the same mould, from the same resin batch, in one run shares its risk source and belongs in one lot.
2. Same truck, different production lots: keep them separate. Two production dates arriving together may still differ in process conditions. Merging lets a bad lot hide inside a good one and destroys the representativeness of the sample.
3. Mixed models: form lots by model. Different models differ entirely in dimensions, liner and assembly, so merging them carries no statistical meaning.

The exception for very small shipments. Where each model arrives in only 20 to 30 units and the total is under about 150, forming a separate lot per model drives the sample close to full inspection and loses the economic point. The workable alternative is a merged lot with stratified sampling: treat the total quantity as one lot, read the total sample size, then allocate samples in proportion to each model's share, with at least one unit drawn for every model. Agree this in the contract in advance; never improvise it on the dock.

Draw samples across the risk positions, not from the top of the stack. Take units from at least three different pallets, different stacking layers and different pack positions, and from different inner cartons where the supplier has used them. Pulling the full sample out of one carton turns sampling into convenience grabbing.

Inspection records and disposition of nonconforming lots

Fields for the inspection record, ready to lay out as a single form:

Agree four disposition paths in advance:

1. Reject and return, for any critical defect or major defects beyond the acceptance number that cannot be effectively screened.
2. Full screening then resubmission, where the defect is detectable, scattered and screening is affordable. A screened lot is re-judged at tightened inspection or zero acceptance.
3. Concession, for minor defects beyond the acceptance number that do not affect function, normally paired with a price adjustment and a written record that applies only to that lot and sets no precedent.
4. Supplier corrective action and a fresh run, for mould or process defects, with a corrective action report and a re-verification plan.

Whichever path is taken, keep the record in writing and file it in the supplier quality record. The value of incoming inspection is not only blocking one bad lot. It is accumulating data that makes visible which supplier repeatedly misses which characteristic. That data drives quarterly reviews and order allocation; for scoring dimensions, see how to build a protective case supplier scorecard.

Judgement calls on the dock and recurring disputes

Dispute one: the supplier says transit caused it. Photograph everything immediately on arrival: outer packaging condition, stretch wrap, seals, stacking layers and the position of abrasion marks. Intact packaging with a scratched case points to the factory. Damaged packaging with regular abrasion concentrated on stacking faces points to transit. Liability ultimately follows the contract, including who arranged carriage, whether insurance was placed, and where risk transfers under the agreed Incoterms rule.

Dispute two: the supplier says the standard allows it. Go back to the agreement and read it line by line. If the agreement only says "appearance shall be good," the real problem is not this case but the agreement. The correct way to close this dispute is to settle the lot commercially and then revise the technical clause, rather than relitigating each shipment.

Dispute three: the two sides measure differently. The cause is usually a difference in tool, method or environment. Sequence the fix. Unify the tool first, with judgement resting on the buyer's calibrated fixture. Unify the method next, using the same standard, the same hold time and the same negative pressure. Unify the environment last, with stable temperature and the same illumination. Only after all three are aligned is it worth questioning the product itself.

Dispute four: one critical defect in the sample. Do not negotiate. Apply zero acceptance and reject the lot. The firmer this rule is held, the more seriously suppliers will control latch assembly and handle attachment.

Segregate at the same time as you judge. A rejected lot should be tagged immediately and moved to a quarantine area so it cannot be mixed with good stock and shipped by mistake. Storage practice for protective cases, including moisture and sunlight control and stacking limits, applies equally to held stock; see warehouse storage rules for protective cases.

Linking incoming data to the supplier quality record

If incoming inspection data is filed and never used, half its value is lost. What pays is turning it into a process profile of the supplier.

Four metrics worth recording:

Suggested switching triggers. After two or three consecutive accepted lots with no critical defects and no major defects beyond the acceptance number, reduced inspection may be requested. Any rejection returns the program to normal inspection immediately. Two consecutive rejections move it to tightened inspection. Both GB/T 2828.1 and ANSI/ASQ Z1.4 contain the corresponding mechanisms, but they only bind if the agreement names them and both parties sign.

Set out the change-triggered retest list at the same time. A new gasket supplier or a new gasket batch, a new resin grade or resin batch, mould repair or replacement, resumption after a long production pause, and replacement of critical tooling should each trigger at least a seal re-verification and, where warranted, a full IP retest. Suppliers whose agreements include these rules generally spend far less on rework than buyers spend on claims.

Inspection intensity by shipment size

The optimal scheme varies sharply with shipment size. The following is a starting point to be tuned against the supplier's history.

The first order must be strict. This is the single most worthwhile rule to hold. The first order is the best window into a supplier's process capability, and relaxing it lowers the baseline for every subsequent lot. For a first order, raise appearance to general level III, sample function and seal at a large fraction, measure every key dimension at first article, and request a complete test document set with retained samples.

Tightened inspection is not a punishment. It is self-protection. It raises discrimination by enlarging the sample so a poor lot has a harder time slipping through. The practice to avoid is quietly lowering the standard when a supplier runs into trouble, in order to protect the delivery schedule. That trades a short-term schedule against a long-term quality liability.

Frequently Asked Questions

Q: How many cases should be sampled on arrival, and is there a fixed number? A: There is no fixed number, only a fixed method. Determine the inspection lot size N, choose the inspection level, normally general level II, read the code letter from the lot size, then read the sample size and accept and reject numbers from the code letter and the AQL for each defect grade. For example, a lot of 1201 to 3200 gives code letter K, a sample of 125, and AQL 1.0 gives 3 accept and 4 reject. A lot of 281 to 500 gives code letter H, a sample of 50, and AQL 1.0 gives 1 accept and 2 reject. So the sample depends entirely on lot size, inspection level and AQL. Two further points: critical defects run at zero acceptance, and destructive samples are drawn in addition and never counted toward lot acceptance.

Q: If appearance is clean, can functional testing be reduced to a token few units? A: Not advisable. Functional scatter is generally wider than appearance scatter because it depends on assembly tolerance, latch and hinge component lots, and operator technique. Appearance asks whether the part was moulded correctly; function asks whether it was assembled correctly. A practical rule is that the functional sample should be at least one third of the appearance sample, never fewer than three units at small lot sizes, and 8 to 10 units at medium and large lot sizes. Safety-related characteristics such as latch retention and handle strength should not be sampled at all but placed on zero acceptance or full inspection. The real saving comes from having the supplier build those checks into the process, not from shrinking the sample at the dock.

Q: Can a pressure decay test replace the IP67 immersion test? A: It cannot replace it, but the two complement each other. Pressure decay is a fast, non-destructive screening method that can cover a large sampling fraction or a full lot and indirectly reflects gasket compression and gasket land flatness. Its limits are that it does not locate the leak and is not fully equivalent to real immersion, particularly for long immersion, thermal cycling and equalisation valve conditions. The recommended combination is a per-lot pressure decay screen plus a type-test immersion confirmation. Run the immersion confirmation to IEC 60529 or GB/T 4208 at design freeze, after material or mould changes, and after a long production pause. The two methods answer different questions and should not substitute for one another.

Q: Several models arrive on one truck. Can they be merged into a single inspection lot? A: In principle no, because the models differ entirely in dimensions, liner and assembly, and a merged sample loses representativeness. The correct approach is to form lots by model, read the table separately and judge separately. The one exception is when every model arrives in very small quantity, for example a combined total under 150 units, where a lot per model pushes the sample close to full inspection. In that case use a merged lot with stratified sampling: treat the total as one lot, read the total sample size, allocate in proportion to each model's share, and draw at least one unit per model. Agree this in the technical agreement or inspection specification in advance, never on the spot, otherwise the sampling process itself becomes contestable.

Q: The supplier says all their products passed IP67 testing. Do we still need per-lot seal testing? A: Yes. A test report proves that the submitted sample met the declared rating at the time of submission. It is type-test evidence and does not mean every production unit conforms. Sealing risk in volume production comes from several directions: batch-to-batch variation in gasket hardness and cross-section, within-lot variation in gasket land flatness, flash trapped under the seal, gasket twist or misplacement during assembly, and low temperature embrittlement of the material. None of these appear in a hand-built sample yet all of them appear at random in production. Run a pressure decay screen on every lot, keep a periodic immersion confirmation on a quarterly or semiannual cycle, and file the reports against the lot number.

Q: A lot fails inspection and the supplier asks us to accept it at a discount. Should we agree? A: It depends on the defect grade. Critical defects cannot be conceded, because they involve safety and loss of the protective function. A lot with major defects beyond the acceptance number can only be considered for concession if the defects are fully detectable, screening is affordable, and the screened lot is re-judged at tightened inspection or zero acceptance. A lot with minor defects beyond the acceptance number that does not affect function can go to concession, provided three conditions hold: a written concession record, a corresponding price adjustment, and an explicit statement that the concession applies to that lot only and sets no precedent. File every concession in the supplier quality record. If the same defect item keeps returning to concession, the problem was never solved and the program should move to tightened inspection or a supplier change.

Q: Packaging arrived intact but the cases are scratched. How is liability assigned? A: Fix the evidence on site first, then discuss liability. Evidence includes photographs of the outer packaging, stretch wrap and seals, a record of stacking layers, photographs of the scratch positions and directions, and photographs of the same position on other units in the lot. The logic runs as follows: intact packaging, no matching abrasion marks and identical marks on several units point to the factory; damaged packaging with regular abrasion concentrated on stacking faces or pallet edges points to transit. Liability ultimately follows the contract, including where risk transfers under the agreed Incoterms 2020 rule, with the seller bearing risk before the named point and the buyer after it. For export orders, also check whether cargo insurance was placed and what the policy excludes.

Q: What happens if the inspection tools are not calibrated? A: Whole-lot verdicts can be wrong. The clearest case is a force gauge: an uncalibrated gauge can be off by more than 10 percent, so a passing handle load test means nothing. Worse, when the two sides use different tools, the argument shifts from whether the product conforms to whose gauge is right, and that cannot be settled by inspection. Write into the agreement that judgement rests with the buyer's calibrated fixture, and that a supplier may request a joint re-test on third-party calibrated equipment. Put calibration intervals in the work instruction as well, with semiannual calibration for pressure gauges and annual calibration for force gauges and length instruments.

Q: How long should inspection records be kept, and do they travel with the goods? A: Send a condensed version with the goods and keep a full version internally. The travelling document serves warehouse and customer traceability and carries the lot number, inspection date, sample size, verdict and inspector signature, usually as a certificate or inspection slip on the pallet or outer carton. The full internal record carries measured values, defect counts and disposition and should be kept at least as long as the product warranty period, with destination market retention requirements added for export orders. Where a customer requires serial-level traceability, mark the lot number on the product itself during production, because no amount of incoming inspection can reconstruct a production lot after the fact.

Conclusion and Related Reading

Back to the original question: for incoming inspection of protective case shipments, four gates plus one table is the complete answer. The gates are documents and markings, appearance and dimensions, function, and the seal check, and the order cannot be shuffled. The table is the sampling plan read from GB/T 2828.1 or ANSI/ASQ Z1.4 by walking from lot size to code letter to sample size and accept and reject numbers. All five elements must be stated; a bare AQL number is not a plan.

Three actions you can take immediately. First, translate the technical agreement into an inspection card so that every requirement becomes an action, a tool and a threshold, backed by one approved sample and one boundary sample. Second, put critical defects on zero acceptance so that latch retention, handle strength and leakage at the declared IP rating never rest on sampling. Third, turn arriving data into a supplier profile using lot acceptance rate, defect density, defect type distribution and disposition distribution. After two quarters of accumulation, order allocation has an objective basis.

JUNZHJIA, manufactured by KeXin New Materials (Guangdong) Co., Ltd., produces protective cases, toolboxes, military-specification storage cases and waterproof junction boxes for wholesale, distribution, OEM/ODM and global supply. The company supports customer incoming inspection programs with lot marking, factory inspection records, material declarations and seal verification data, and folds sampling plans, acceptance bases and change-retest rules into the technical agreement so that the receiving dock judges from documents rather than from impressions.

Related Reading

• Acceptance criteria for custom protective cases: AQL sampling and factory inspection
• How to verify IP67: test reports and practical methods
• Warehouse storage rules for protective cases