Cal. Pub. Res. Code § 18015

(a) All rigid plastic bottles and rigid plastic containers sold in the state shall be labeled with a code that indicates the resin used to produce the rigid plastic bottle or rigid plastic container. Rigid plastic bottles or rigid plastic containers with labels and basecups of a different material shall be coded by their basic material. The code shall consist of a number placed inside a triangle, and letters placed below the triangle. The numbers and letters used shall be as follows:
1 = PETE (polyethylene terephthalate)
2 = HDPE (high density polyethylene)
3 = V (vinyl)
4 = LDPE (low density polyethylene)
5 = PP (polypropylene)
6 = PS (polystyrene)
7 = OTHER (includes multilayer)
(b) A “7” shall appear below the resin abbreviation when the bottle or container is composed of more than one layer of that resin.
(c) The Division of Recycling in the Department of Resources Recycling and Recovery shall maintain a list of abbreviations used on labels pursuant to subdivision (a) and shall provide a copy of that list to a person upon request.
(d) The resin identification code required pursuant to subdivision (a) shall not be placed inside a chasing arrows symbol, as defined in subdivision (f) of Section 17580 of the Business and Professions Code, unless the rigid plastic bottle or rigid plastic container meets the statewide recyclability criteria provided in subdivision (d) of Section 42355.51.