Decoding the UN Packaging Mark: Every Field on a 4G Box Explained

The dangerous-goods desk at the forwarder sends back one line: "Mark reads Y25, package weighs 27.4 kg." Nothing is wrong with the box. Nothing is wrong with the UN packaging mark printed on it. What went wrong is that the person who specified the carton read "25" as the weight of the product going inside, when the field means the maximum gross mass of the finished package — box, cushioning, inner bottles, closure tape and substance, all of it. The 2.4 kg of packaging that made the shipment safe is the same 2.4 kg that made it non-compliant.

That is the whole problem with the UN mark. It is short, it is printed in one line, and every character in it is a load-bearing statement about what the packaging was tested as. Reading it correctly takes about ninety seconds. Reading it incorrectly is invisible until someone at a port or a carrier reads it properly.

The mark is a sentence with a fixed word order

The UN Model Regulations set out the elements of the mark and the order they appear in, and the national and modal rules — ADR/RID in Europe, the IMDG Code at sea, the ICAO Technical Instructions in the air, 49 CFR in the United States — carry the same structure through. A complete mark on a fibreboard box for solids or for inner packagings looks like this:

⒰⒩ 4G/Y25/S/26/CN/[manufacturer identification]

Broken into fields:

The elements may be applied in one line or across several, and the mark may be printed, stencilled, embossed or applied on a durable label — but the sequence has to hold. A mark that reorders the fields, or that omits one, is not a shorter version of a valid mark. It is a different string that means nothing.

Character size is also regulated rather than aesthetic. The commonly cited thresholds are 12 mm minimum character height for packagings above 30 litres or 30 kg, 6 mm at or below that, and a smaller minimum for very small packagings. Verify the current figures before you write them into a drawing, but do write them into the drawing — a print supplier scaling your mark to fit a design element is a real failure mode, and it is one you can catch on the artwork proof rather than on the dock.

Field 2 in detail: what "4G" actually names

The identification code is three positions, not two, even when only two are used.

First position — kind of packaging. 1 drum, 3 jerrican, 4 box, 5 bag, 6 composite packaging, 0 light-gauge metal packaging. There is no 2 in current use.

Second position — material. A steel, B aluminium, C natural wood, D plywood, F reconstituted wood, G fibreboard, H plastics, L textile, M paper (multiwall), N metal other than steel or aluminium, P glass, porcelain or stoneware.

Third position — category, where one exists. Drums use it heavily (1A1 non-removable head, 1A2 removable head). Fibreboard boxes do not need it, which is why 4G is only two characters, while a plastics box is 4H1 or 4H2.

So 4G is a fibreboard box, and it sits alongside 4C1 and 4C2 (natural wood), 4D (plywood), 4F (reconstituted wood) and 4H1/4H2 (plastics) as an outer packaging option for the same combination package. If a supplier quotes you "UN box" without naming the code, you have not been quoted a design type — you have been quoted a category.

The letters that follow the code: V, U and W

A code sometimes carries a trailing letter, and this is where the operationally useful detail lives.

• 4GV — a variation packaging tested to special provisions with cushioning and a defined mass of inner packagings. A V-marked box lets you vary the inner packagings within the tested envelope rather than re-testing a design type for every bottle size. For a buyer shipping a range of SKUs in one outer, this is the difference between one design type and eleven.
• 4GU — a special packaging for infectious substances, tested to a separate regime.
• 4GW — a packaging that differs in construction from the standard specification but has been shown equivalent and approved by a competent authority.

None of those letters is decorative, and none is a marketing upgrade. If you need the flexibility a V packaging gives, you have to specify it at the enquiry stage, because it changes what the design type was tested with.

The three fields buyers get wrong most often

The performance letter. X, Y and Z run one way only. An X design type may be used for packing groups I, II and III. A Y covers II and III. A Z covers III alone. Buyers reliably read this as a quality ladder and assume a Y box is "better than needed" for a packing group II substance — it is exactly what is needed, with no margin above it. Nobody is protected by a Z box carrying a packing group II substance, and nothing about the box's physical appearance will tell you.

The mass field. As in the opening example, 25 is the maximum gross mass of the complete package. Work backwards from it: subtract the tare of the outer box, the cushioning, the inner packagings and their closures, and what remains is your permitted net fill. On a well-cushioned 4G with glass inners, tare can be a fifth of the rated gross mass. Specify from the gross figure down, and the arithmetic stays honest.

The S. S says the packaging is intended for solids or to hold inner packagings. On a 4G box that also carries liquid in inner bottles, S is correct — the box is the outer of a combination packaging, and the liquid-tightness lives in the inners. Where S is wrong is on a single packaging you intend to fill with liquid directly; that mark carries a hydraulic test pressure in kPa instead. If you are looking at a box mark and expecting a pressure figure, you have confused the two package architectures.

Year, state and manufacturer: the fields that say who stands behind it

The last three fields are the traceability chain, and they are the ones an inspector uses when something has gone wrong.

The year is the year of manufacture, not the year of certification and not an expiry date. Design types are requalified on their own schedule; the year on the box tells an inspector how old that specific box is, which matters because fibreboard ages, absorbs moisture and loses compression capacity in storage. A carton made in a humid warehouse two years before you fill it is not the carton that was drop-tested.

The state code names the competent authority under whose authorisation the mark was applied. CN means the Chinese authority; USA means the United States. This is a statement about who authorised the mark, not a statement that any given destination will treat the packaging as compliant with its own domestic rules. Those are different questions and they have different answers, which is the subject of the US-side obligations covered separately.

The manufacturer identification is a name, or a symbol or code that the competent authority has specified. In the United States, a symbol used in place of a name has to be registered with the regulator, which is why US-market marks often end in an alphanumeric registration code rather than a company name. Whatever appears there, it is the field that lets you connect a physical box back to a design-type test report. If the last field on a sample box is blank, illegible or a generic string, the traceability chain is broken before you have started.

What the mark does not tell you

This is the part that costs buyers money, because the mark is compact enough to feel like a complete answer.

The mark does not tell you which inner packagings the design type was tested with. A 4G design type is a tested system: outer box, specified inner packagings, specified cushioning and specified closure, qualified together. Swap a 500 ml HDPE bottle for a 500 ml glass one and you are outside the tested design type even though the mark on the outer box has not changed a character.

It does not tell you how the box must be closed. Tape width, tape type, number of strips, flap sequence and staple pattern are part of the tested configuration and are communicated separately, in the manufacturer's closure instructions.

It does not tell you when the design type was last requalified, whether the test report covers your dimensions, or whether the substance you are shipping is compatible with the packaging materials.

And it is not hazard communication. Hazard diamonds, the proper shipping name, the UN number, orientation arrows and any supply-side labelling are a separate layer with separate rules — including rules against a package carrying marks or labels for a substance it does not contain. A carton printer can print all of it on the same pass, which is convenient and also means one artwork file now controls two independent compliance systems. Check them as two files, not one.

Where to send these questions

The CMH listing for Jindong Packaging, a Shenzhen paper-packaging manufacturer operating from a 12,000 m² plant in Xinqiao, Bao'an since 2007, names dangerous-goods (UN) cartons among its product lines alongside heavy-duty and export corrugated cartons, and describes hazard diamonds and handling marks as printed items. It also states that board is produced in-house on automatic corrugated lines and that work is done ODM, to a buyer's drawing or sample.

What that listing does not state — and what you therefore have to obtain in writing from any supplier, this one included — is which design types exist, what their identification codes and mark strings are, what performance level letter and rated gross mass they carry, which inner packagings and cushioning they were tested with, which competent authority authorised the mark, and whether the authorisation is current. Treat all of that as an open request. The same discipline applies to reading any document that comes back: knowing what a China-issued certificate does and does not cover is the difference between a document and evidence, and a broader China import compliance walkthrough will tell you which of your own filings depend on the answer.

Common questions

Does the UN mark expire?

The mark itself carries a year of manufacture, not an expiry date. What has a validity period is the design-type qualification behind it, under whatever regime the authorising state operates, and the periodic retest schedule that regime imposes. Ask for the requalification date and the retest interval as separate items from the mark string.

Can a supplier print a UN mark on a box that has not been tested?

Applying the mark is a statement that the packaging conforms to a successfully tested design type. Doing it without that basis is a regulatory offence in every jurisdiction that has adopted the model regulations, and it is also the single hardest thing for a buyer to detect visually — printed marks look identical whether or not a report exists behind them. This is why the test report, not the printed box, is the artefact to ask for.

My substance is packing group III. Should I just buy an X-rated box to be safe?

You can, and it is authorised, but you will pay for board and construction you do not need, and the higher rating does not remove any of your own duties. Match the letter to the packing group, then spend the difference on cushioning and closure discipline, which is where combination packagings actually fail.

What to ask your packaging supplier next

Send these with the enquiry, before any drawing is quoted, and file the answers with the purchase order:

1. Write out the complete mark string you would apply to my carton, field by field, including the authorising state code and the manufacturer identification.
2. Which packaging identification code — 4G, 4GV or something else — and if not a V packaging, what would it take to qualify one for my SKU range?
3. What is the rated maximum gross mass, and what is the tare of the outer box, cushioning and inner packagings so I can calculate permitted net fill?
4. Send the design-type test report naming the inner packagings, cushioning and closure used, the testing laboratory, and the date.
5. Send the closure instructions as a document, not as a sentence in an email.
6. Which competent authority authorised the mark, what is the reference, and when is the next requalification due?
7. Separate the artwork files: performance mark on one layer, hazard communication on another, with sign-off on each independently.

Jindong Packaging is one place to run that list — a CMH-listed Shenzhen carton maker working to drawing or sample on an ODM full-material basis, with sampling quoted at about seven days and bulk production at about fifteen working days from 1,000 pieces on T/T terms. Ask it the same seven questions you would ask any other supplier, and judge the answers on specificity: a supplier that returns a complete mark string and a test report reference is telling you something a printed box cannot. Pairing that with a standing list of documents to request before a first order and the narrower document set to demand when buying UN certified boxes keeps the paperwork moving at the same speed as the sample.