Storable sacks are a type of container that is designed to be easily stored and transported. They are often made from a lightweight material such as canvas or nylon, and feature a drawstring closure at the top. COTS is an acronym for 'Collapsible Open Top Storage, ' which is a type of storable sack that can be folded down for easy storage when not in use. These sacks are popular for camping, hiking, and other outdoor activities, as they provide a convenient way to store and transport items.