LOCK & LOCK GLASS, 4.0 Cup, Borosilicate Glass, Oven Safe, BPA Free, 100% Airtight, Glass Round Food Storage Container with Lid PATENTED LOCKING SYSTEM: Lock & Lock containers are guaranteed leak-proof (airtight and watertight) with our patented four-hinge locking system and silicone sealing lid. This assures food to stay fresh longer and keeps contents in containers secure. HEAT RESISTANT GLASS: Made from borosilicate glass that can withstand heat up to 750 F and is thermal shock resistant up to 248 F. Safe enough for storing and cooking without the risk of spontaneous breaking & shattering. CONVENIENT TO USE: Safe to use in the oven (without lid), microwave, freezer and dishwasher. From oven to table and from freezer to microwave, Lock & Lock glass containers are versatile and convenient to use. Wide variety of unique, stackable designs allows you to save space in your cabinets, refrigerator, and freezer. PRODUCT OF THE YEAR: Winner of Product of the Year, 2010 (UK) and Red Dot Design Award, 2011 (Germany). ONLY LOCK & LOCK PRODUCTS "SOLD BY" AMAZON or LOCK & LOCK ARE GUARANTEED GENUINE