Based on the compression dry sack, the main body fabric is made of 30D ultra sill nylon, and the 40 Percentage is also lightweight. The waterproof and breathable eVent fabric on the bottom is designed to keep water out when air is escaped. Air from the bottom by rolling the opening through the opening rather than compression caused by valves or strap tightening. It protects bulky gear such as thermal wear and sleeping bags from water and is perfect for compact storage of your luggage. Oval bottom flattens flat to fit the inside shape of the backpack. Double-stitched + seam tape treatment for superior waterproofing Buckle release for quick access Hypalon material roll top prevents moisture from entering. Waterproof breathable material prevents air from escaping and moisture intrusion. Comes with a handle on the bottom for convenient removal from the backpack