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 moulded 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 and remain tight. The Classic Lock ; Lock comes in a wide variety of shapes and sizes and uses. The BPA free polypropylene can withstand temperatures from -20 to 100oC and is dishwasher, freezer and microwave safe.