Lock & Lock is simply the best storage containers you will ever buy! The patented four-point locking system, often copied but never matched, features a silicon seal and is 100% leak and air tight. The locking Tabs are tested to millions (literally millions!) of closures and will not snap or break. The Euro glass range is made from hardened borosilicate glass and is leak-proof, air tight, microwave and freezer safe and ovenproof up to 400oC YES thats 400oC!! It is lighter than traditional tempered glass and will not shatter from thermal shock so you can take it from a freezer and put it directly into a hot oven. Unsurprisingly it has a limited lifetime warranty.