Featuring a unique 4-hinge locking system for freshness that lasts longer, LocknLock Performance Glass storage containers are constructed from borosilicate glass, which can withstand both high heat and sudden cooling but is 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 LocknLock Performance Glass containers are microwave, freezer, oven, and dishwasher safe. (Lid not intended for oven use). Always BPA-free, LocknLock Performance Glass containers are stain and odor resistant, easy to clean, and come with a Lifetime Limited Warranty for healthy, happy, no-worries food storage that's great for leftovers, too.