HIGH QUALITY BOROSILICATE CRYSTAL CLEAR GLASS BODY, The containers are made of borosilicate glass because it is much stronger and can hold up to temperature changes much better than the cheaper glass food storage containers. BPA FREE AND FDA APPROVED so it will not affect the food inside the food container. MICROWAVE, OVEN, FREEZER, & DISHWASHER SAFE - easy to be heated, storage, and cleaned,including oven up to 1112°F and freezer down to 104'F. Borosilicate properties allow to 248°F temperature change, DO NOT use lids in the oven.