Platinum silicone is made primarily from sand (silica) & oxygen and contains no added fillers, polymers, or by-products. Stasher bags and bowls can be safely subjected to heat and are safe to cook, freeze, and run in the dishwasher! We regularly test our material sourcing and are proud to say that we not only comply with FDA standards but also pass stricter EU food-grade standards, yay! EU food standards do not allow any silicones with fillers to come into contact with food.