Silicone Food Storage Bags is made of food grade silicone, no any the poisonous chemicalsHermetic Seal - Leakproof vacuum and a zip-locked container that can store all kinds of solids and liquids without spilling Hermetic seal to store liquids or solids. (NOTE: When you start to use it for first several times, the lock for the bag may a little tight seal, thats for a special purpose to make the best effect of preservation.)Temperature Resistant - Heat and cold resistant, temperature resistant -58℉~482℉(-50℃～+250℃), safely used in a microwave o