Featuring a 4-hinge locking system for freshness that lasts longer, Lock and Lock Purely Better 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 leak-proof lid has been durability tested to last up to 3 million uses, and Lock and Lock Purely Better glass containers are microwave, freezer, oven, and dishwasher safe. Always Bpa-free, Lock and Lock Purely Better containers are stain and odor resistant, easy to clean, and come with a Lifetime Limited Warranty for healthy, happy, no-worries food storage.