By popular demand! This container fits as an insert into USPS' large Priority Flat Rate and Service Personnel boxes. Now perishables and other temperature sensitive items (such as chocolates, cakes, burgers, sausages, flowers, or medications) can be mailed at a flat rate in a temperature controlled environment. Simply, place the item(s) you want to ship in the recommended poly bag liner, place that bag in the container, surround the bag with our leak-proof ICE-BRIX.