The containers are scientifically designed for stacking both upward and sideways to save space on the shelf.\n\n1. Airtight Lockage\nIt has passed the leakage tests by authoritative local and international institutes. 4-side of locking system makes it possible to be airtight due to equal pressure to all 4 sides. Strong airtight lock with hollow-center silicone. Airtight seal with great elasticity power locks tightly with hollow-center silicone.\n\n2. Durability\nIt has passed the KEMTI‘s bending test. The container and the wing were fixed to the bending test machine and bent. 3,000,000 times 80 degrees left to right. If the container were to be used 10 times a day, it could be used for 821 years(semi-permanently). Durability is safe for change of temperature from -4°F to 210°F. So it can be used in the microwave, freezer and dishwasher.\n\n3. Healthful living\nIt is made up of superior raw material with durability and heat-resistant ability which is friendly to the human body. Passed the strict hygiene and safety tests of U.S. FDA and German SGS.\n\n4. Space Saving Design\nStacking system aims to help space saving. The design of the containers enables excellent space saving in the refrigerator, freezer, cupboard and drawers.