Can the UN mark be printed on a label and applied afterwards?

No. The mark must last as long as the case, and adhesive lifts after a 3 m stack or a 1.2 m drop. We mould raised or recessed characters at 12 mm minimum, or hot-stamp a plate area.

Can one case carry both X and Y?

No. A mark states one group. X may be used downward, but the character stays single. Two groups mean two tools, not two letters on one wall.

Is drop height based on the empty case or the gross mass?

Gross mass: case, insert and contents, exactly what segment 4 reports. A 25 kg unit drops at 1.2 m, and a 40 kg unit still drops at 1.2 m, but the stack tier count is recalculated.

Does 3 m stacking mean the case can be stacked 3 m high?

No. 3 m is a test load equivalent to similar packages stacked that high. Real tiers depend on unit mass and pallet rating.

Should the case show the UN number of the goods?

No. The goods number belongs to the shipment and appears in the transport marking applied by the shipper. The case mark has no goods-number segment, and the two systems stay apart.

ADR Packaging for Cases

Quick answer: adr packaging status rests on one line of code: six UN segments plus the drop, stack and leakage tests behind the X, Y or Z class.

One Line of Code Decides the Status
Reading UN 4G/Y25/S/26/CN/1234
X, Y and Z: Three Drop Heights
Four Tests, Two of Them Optional
Marking, Report, Quality Record
FAQ

1. One Line of Code Decides the Status

A moulded case can hold 40 kg and survive a fall down a stairwell, and still be a plain tote on paper. What separates the two is a line of characters moulded into the wall. ADR 4.1.1.1 is blunt about it: packaging for dangerous goods must meet a defined performance level and carry the matching mark on every finished unit.

The mark is not decoration. It is the case's identity.

Segment	Meaning	Example	Typical error
1	UN packaging symbol	UN	printed as EU, or as a bare square
2	Box code	4G	4H2 and 4G swapped
3	Packing group letter	Y	Z moulded, group II declared
4	Maximum gross mass	25	pounds written instead of kilograms
5	Contents form	S	liquids marked S
6	Year, country, maker	26/CN/1234	year one off the batch record

Segment 3 is the one that gets edited. Move the letter and nothing physical changes, yet the declared group slides from II to III and the drop height falls from 1.2 m to 0.8 m. The test report still reads the same. The case no longer does.

2. Reading UN 4G/Y25/S/26/CN/1234

The order never varies. A moulded case maps to 4H1 or 4H2, with 4H2 adding a sift-proof requirement; the 4G on the sample belongs to fibreboard, and the sequence reads the same.

adr packaging units stacked on a wooden pallet, twelve beige cases with two latches each, green floor and yellow rack behind

Segment 4 carries gross mass in kilograms, meaning case plus insert plus contents, not the empty shell. Gross mass fixes the drop height, and it also fixes how many tiers a stack can hold.

Segment 5 describes what may go inside. S suits solids or inner packagings; a case for liquids changes that letter. Get it wrong and the whole line is void, because the letter states the form the shell is approved to hold.

Segment 6 packs three facts: two digits of year, two letters of country, then the maker's number. This is what an inspector checks against the batch file. A year written one digit back turns an entire shipment into expired stock.

Character height runs 12 mm minimum on every finished unit, not on a carton label. Each case travels alone.

3. X, Y and Z: Three Drop Heights

The packing group comes from the shipper. The case maker does not decide it, only builds to the group it is given. On the mark the group appears as X, Y or Z; on the test floor as three drop heights.

Group	Letter	Drop height	Stack
I	X	1.8 m	3 m for 24 h
II	Y	1.2 m	3 m for 24 h
III	Z	0.8 m	3 m for 24 h

The gap between tiers is not only height. A 1.8 m fall lands about 1.22 times faster than 1.2 m and carries roughly 1.5 times the energy, so the wall moves from 3 mm to 4.5 mm, latches go from 2 to 4, and base ribs rise from 6 mm to 10 mm. At 0.8 m the wall may drop to 2.5 mm, but the stack requirement never relaxes.

All three stack at 3 m for 24 h. Stacking tests creep under sustained load rather than impact, which is why a case that passes the drop and fails the stack is rejected.

4. Four Tests, Two of Them Optional

Drop and stack apply to every case. Hydraulic and air tests apply only to packagings that hold liquid.

adr packaging tooling: rows of dark steel injection moulds on a shop floor, lifting eyes and water lines, red crane beam with yellow hoist above

The drop runs face, edge, corner on one specimen; afterwards the case is opened and the insert checked for shift. The stack puts a 3 m equivalent load on the lid for 24 h and measures residual set.

Test	Condition	Pass line	Who needs it
Drop	1.8 / 1.2 / 0.8 m by group	no leakage, no spill	every case
Stack	3 m for 24 h	no collapse, no permanent set	every case
Hydraulic	100 kPa	no leakage	liquid packagings
Air	30 kPa	no bubble release	liquid packagings

For those two the work sits in the tool: no weld line through a wall, gate off load-bearing faces, base radius at 5 mm or more.

5. Marking, Report, Quality Record

A case offered as outer packaging hands over three items, and a missing one stops the inspection. First, the UN mark on the wall: six segments, 12 mm characters, every unit. Second, a performance report whose test items match the group and whose box code matches the hardware. Third, a production quality record listing batch, resin grade, tool number and date of marking.

The three have to line up in time. A report from 3 years ago, a tool that had its gate moved since, and a record that cannot bridge the two will send the shipment back for retesting.

The transport assessment and declaration are issued by a licensed body; the case carries the outer packaging and fixing duty only. Put that on the quotation and in the drawing notes, because it decides who reads which document after an incident.

Conclusion

Whether a case serves as outer packaging sits in six segments: UN, 4G or 4H2, Y, 25, S, 26/CN/1234. Change the group letter and the drop height follows at 1.8 m, 1.2 m or 0.8 m, while the 3 m / 24 h stack holds for all three. Line up mark, report and quality record, and the case earns the status rather than claiming it.

This article covers case-side specifications only and does not address any handling, loading or use of the contents.