Stickers can be made of different plastics, including: Polypropylene: it is our most popular plastic material. It is waterproof, tearproof and oil resistant, perfect for food, beverage and cosmetic products. Polyester: we offer this material for our heavy duty printable labels as it is better suited for outdoor usage. Polyethylene: this is our most resistant plastic material, it will resist to almost anything (it is even certified to resist to 90 days in sea water!)