Heat resistant and airtight ,on select models with four locking system. It uses material that contains strong heat resistant properties which could withstand sudden change in temperature. Plastic lids are BPA free. Our heat-resistant glass is produced in temperatures above 2900 F which makes it harder to manufacture, but safer to use. This product is thermal shock strength is 248 F. Our heat resistant glass can be used not only in a refrigerator, a microwave, and a dishwasher, but also in a 750 F conventional oven. Unlike normal or tempered glass, if the item gets broken by physical shock, it doesn't break into numerous fragments and scatter. Therefore, it is safer and more suitable for you and your family. Cook in the oven with or use it as bakeware ,without lid. Microwave safe. It is salt and oxidation resistant and stain and odor resistant.