Featuring a patented 4-hinge locking system for freshness that lasts longer, LocknLock Purely Better storage containers are constructed from borosilicate glass, which can withstand both high heat and sudden cooling but are 10 percent lighter than tempered glass for easy, on-the-go use. The airtight and leakproof lid has been durability tested to last up to 3 million uses, and features an innovative steam vent to prevent pressure build-up when foods are heating or reheating. Plus, LocknLock Purely Better glass containers are microwave, freezer, oven, and dishwasher safe. LocknLock Purely Better containers are also stain and odor resistant, easy to clean, and come with a Lifetime Limited Warranty for healthy, happy, no-worries food storage.