How is the internal size of a plastic box container measured?

Answer: At the narrowest point, three readings per axis, take the smallest. Where the base has ribs, height runs from rib top to rim.

Do clear boxes crack more easily?

Answer: Clear resin is about ten percent less tough in a one-metre drop; heavy loads want natural resin at 2.0 mm.

How many layers are safe?

Answer: Three loaded, five empty. At 25 kg a layer, keep the bottom load under 75 kg.

Can a broken latch be replaced?

Answer: Catch types yes, two screws and three minutes each. Moulded cams mean a new lid.

Does a custom colour cost extra?

Answer: Yes. Purging adds 200 to 400 CNY below 500 pieces.

How to Choose a Plastic Box Container: Five Checks

Quick answer: Judge a plastic box container on five checks: resin and light transmission, internal clear size, stacking and shelf access, latches and sealing, unit cost. The first two are hard limits; the rest explain the price gap.

Five Checks for a Plastic Box Container
Check One on Resin and Light Transmission
Check Two on Internal Clear Size and Dividers
Check Three on Stacking and Shelf Access
Checks Four and Five on Latches Sealing and Cost
FAQ

1. Five Checks for a Plastic Box Container

Most rework comes from the order of the questions. Buyers pick a colour, measure the inside, then find the box will not fit the shelf.

Check	What to measure	Target	Usual mistake
Resin and light	grade, wall thickness	1.5 to 3.0 mm	colour over wall
Internal size	length, width, height	plus or minus 2 mm	outside read as inside
Stacking	layers, hand clearance	3 loaded layers	floor only
Latches	count, holding force	120 N each	catch read as seal
Unit cost	price, tooling share	cost per thousand	price only

The first two are hard limits: get them wrong and the batch goes back.

2. Check One on Resin and Light Transmission

Polypropylene resists chemicals and washes clean; 1.5 mm suits light loads, 2.0 mm is the general grade, 3.0 mm survives stacking. A clear box allows stock counts without lifting the lid, at a UV cost.

Plastic box container: a clear box open with two lid catches, holding a green circuit board, USB adaptors and coiled red and black cables

A drop test separates the walls. With a 1.5 kg head from one metre at 0 °C, a 1.5 mm box usually cracks, a 2.0 mm box passes, a 3.0 mm box takes a dent. A warehouse at 0 °C behaves one grade worse than 20 °C, so specify against the cold figure.

3. Check Two on Internal Clear Size and Dividers

Internal clear size is where a plastic box container is most often overstated. An outside size of 480×350×250 mm loses wall, ribs and lid boss, leaving 455×325×220 mm inside, roughly thirty percent less volume.

Nominal	Outside	Internal clear	Suited to
20 L	480×350×250 mm	455×325×220 mm	cable, small parts
35 L	560×400×300 mm	535×375×270 mm	tools, matched sets
60 L	650×450×350 mm	620×420×320 mm	spares, consumables
100 L	780×560×420 mm	745×525×390 mm	machine accessories

Ask for the tolerance: moulded interiors run plus or minus 2 mm, so two boxes can differ by 4 mm, which shows in a rack row. Dividers add up too, at 4 mm each, six compartments eat 20 mm of width.

4. Check Three on Stacking and Shelf Access

An empty plastic box container stacks five high; loaded at 25 kg a layer, the bottom lid carries 75 kg at the fourth layer and starts to dish within six months. Three loaded layers is the safe line.

Plastic box container: a grey box open on a wooden bench, foam cut-outs in the lid, coiled cables and black power units beside it

Stacked six high at 300 mm, the top handle sits 1.75 m off the floor, above the reach of a 1.6 m operator, so fast movers belong between 0.6 m and 1.4 m. A 90×50 mm matt panel takes marker pen and wipes clean; without it, labels curl off in three months.

5. Checks Four and Five on Latches Sealing and Cost

Latches decide sealing and whether a box opens in transit. At 120 N holding force, two opposed latches beat four small catches because the load sits on the outer walls. For dust, a standard catch reaches IP54; IP65 needs a foam gasket.

Item	Light	General	Heavy
Wall	1.5 mm	2.0 mm	3.0 mm
Latches	two catches	two catches, rib	two cams
Seal	none	one foam line	two foam lines
Loaded stack	2 layers	3 layers	4 layers
Price per 1000	18 to 24 CNY	26 to 34 CNY	above 40 CNY

Cost belongs per thousand. One mould serves all three levels, and tooling over a 500-piece minimum adds 3 to 6 CNY per unit; at 2000 pieces the unit drops about fifteen percent, but lead time stretches from 22 to 35 days.

Conclusion

Choosing a plastic box container is five checks in sequence: resin, clear size, stacking, latches, cost. The first two cost a whole batch when wrong; the rest only cost money. Settle them first, and the plastic box container fits the rack, the load and the budget.

This article discusses only the container (case body) side of specifications and design intent, and does not cover any handling, loading or use of the contents.