Made from Polypropylene & Silicone and are BPA free. Unique 4 side patented locking system. Eco friendly. Tighter seal while maintaining an easy open & close.100% air and liquid tight. Seal remains tight after repeated use Flexible and durable hinge - passed 3 million times of a hinge working test. Can withstand temperatures from -20°C to 100°C.Economical as keeps food fresh for longer than competitor product Lid and base are both Dishwasher, Microwave and Freezer safe. Material and composition: Plastic Silicone