Each plastic type is identified by a Resin Identification Code (RIC #1-7).

Plastic Type (Common Name)	RIC	Key Properties	Common Food Uses
Polyethylene Terephthalate (PET or PETE)	#1	Clear, strong, good gas & moisture barrier.	Beverage bottles, salad dressing bottles, oven-safe cooking bags.
High-Density Polyethylene (HDPE)	#2	Stiff, chemical-resistant, good moisture barrier.	Milk jugs, cereal box liners, retail shopping bags.
Polyvinyl Chloride (PVC)	#3	Clear, flexible, good barrier to oils/gases.	Rare for direct food contact today due to plasticizer concerns. Was used for cling film.
Low-Density Polyethylene (LDPE)	#4	Flexible, tough, good moisture barrier.	Bread bags, produce bags, squeeze bottles, frozen food bags.
Polypropylene (PP)	#5	Semi-rigid, high heat resistance (microwave-safe), chemical resistance.	Yogurt containers, syrup bottles, reusable food containers, microwave-safe bags.
Polystyrene (PS)	#6	Rigid or foamed (Styrofoam).	Disposable plates/cups, egg cartons. Not common for bags.
Other (Often Polyamide/Nylon or EVOH)	#7	Engineered for performance.	Multi-layer vacuum bags for meats, cheese (barrier layer), boil-in-bags.