Our snack containers use a pure food-grade silicone that meets FDA and NSF testing requirements. It's non-stick, flexible and easy to clean, and doesn't dry out and crack with use! Our silicone lids are dishwasher safe and oven safe up to 400 degrees Fahrenheit (204 degrees Celcius). The silicone lids are also freezer safe, but beware because it's risky to freeze in our steel containers. Liquids swell when frozen and if the steel container is overfilled the freezing will split the steel.