What the code is
Resin identification codes are a numbering system that identifies the main plastic an item is made from. The number sits inside a triangle of arrows, usually molded into the base of a container or the underside of a lid, often with letters beside it. The arrows make it look like a recycling symbol, which is the source of most confusion: the code tells a sorter or a user what the material is, not whether the item will be collected or recycled where it is thrown away.
For a buyer the code has a more immediate use. It is a material marking on the physical part, and it should agree with everything else in the file. A lid marked 5 is PP; if the specification or the declaration says PET, one of them is wrong, and it is better to find out on the sample than at a retailer's audit.
The seven codes
| Code | Material | Where it appears in this range | Heat and use notes |
|---|---|---|---|
| 1 | PET | Clear fruit boxes, cold drink cups and bowls, fridge bins, some cosmetic organizers, gift box windows | Best clarity; cold use, not for hot food or the microwave |
| 2 | HDPE | Pet food bins | Tough, opaque; storage use |
| 3 | PVC | Clear windows on paper and gift boxes, soft clear pouches for small items | Non-heated packaging and storage only; never a hot food container |
| 4 | LDPE | Films and flexible parts | Soft, flexible |
| 5 | PP | Takeout boxes, soup cups, bowls, divided trays, collapsible boxes, shoe boxes | The heat-tolerant choice; microwave use per supplier marking |
| 6 | PS | Clear drawer organizers and desk trays | Clear and rigid; storage use |
| 7 | Other | Copolyester vacuum containers, acrylic organizers, blends | Code 7 groups many materials; the declaration names the actual one |
Code 5 and the takeout box
Most food containers in this range carry a 5. Export soup cups from a thermoforming partner plant in Guangdong, from 350 ml at 116x99x45 mm to 950 ml at 117x82x141 mm, have the PP code 5 molded into the base together with a microwave marking, both stated by the supplier. Divided trays from the same family carry a microwave safe emboss on the lid, again the supplier's marking. Two different things are happening on that base. The 5 identifies the resin. The microwave mark is a use instruction that the desk checks with a heating test on the sample, lid removed where marked, and writes into the specification. One does not prove the other.
Code 3 and where PVC belongs
A 3 on a part means PVC. In this range PVC appears only in non-heated packaging and storage: clear windows and lids on paper bakery and gift boxes, which do not touch hot food and are not heated, and soft clear pouches for small items. It is not used for food containers. PVC carries a higher migration risk when heated, which is why reputable food packaging plants avoid it in containers meant for the microwave. If a sample food container arrives marked 3, the desk stops and checks the material before anything else. See where PVC belongs in packaging.
Codes 1, 2 and 6 in storage lines
Storage and organizer lines spread across more codes than takeout. Clear fridge bins are PET or PP, so either a 1 or a 5 is correct, as long as it matches the specification. Pet food bins are PP or HDPE, a 5 or a 2, with a separate seal ring that has its own material. Clear drawer organizers and desk trays are often PS, code 6, chosen for clarity and rigidity rather than heat. None of these lines is heated, but the fridge bins and pet food bins hold food, so their codes and declarations still need to agree with each other.
Code 7 and blends
Code 7 is a catch-all. Copolyester vacuum containers, acrylic organizers and many multi-material items fall here, so a 7 tells you almost nothing on its own. Starch-based containers raise the same issue from the other side: the partner plant literature describes them as corn starch filed under PP thermoforming, so the desk treats them as a starch and PP blend, and the marking on the part and the declaration should both reflect that rather than suggest a plant-based material with no plastic content.
Codes and claims are different things
Because the arrows suggest recycling, a resin code can be read as a recyclable claim. In the US, environmental claims on packaging are assessed under the FTC Green Guides at 16 CFR 260, which address recyclable claims separately from degradable and compostable ones and expect each claim to be backed and, where needed, qualified for the market where the item is sold. The desk therefore uses the code as a material marking only and does not add recyclable wording to lids, sleeves or listings unless the brand and its counsel have confirmed that the claim is supported for the market. The same caution applies to degradable and compostable wording; see biodegradable claims and the Green Guides.
How codes get onto the part
On injection molded containers the code is cut into the mold, usually on the base, so it appears on every piece. On thermoformed items it is formed into the sheet by the tool. Changing a code or adding a brand mark to the base is therefore a tooling change: cheap on a new mold, possible on some stock molds with an insert, and impossible on others. Printed sleeves and cartons can repeat the material, which is helpful for retail, but the molded code is the one that stays with the item. Tooling options are covered in injection molding.
A sample check in five steps
- Read the code on every part of the sample.
- Compare it with the material on the specification and on the declaration.
- Check that the use instructions on the part, such as microwave marks, match tested results.
- Remove any recyclable or degradable wording from artwork that the evidence does not support.
- Record the codes and photos in the program file for repeat orders.
Custom base markings on a new mold sit inside the new mold minimum, typically from 50,000-100,000 pieces per item, confirmed in writing per program; see MOQ and lead time. Send the item list through the quote form, and the desk will return each model with the material and code of every part.