Sea to Summit eVAC Dry Sack nylon 3-Liter: 11 x 7 x 4-inch; 5-Liter: 15 x 7 x 4-inch; 13-Liter: 20" x 9" x 6" Air permeable, waterproof event fabric base Valve-free air expelling design for compact packing Space saving, low profile, streamlined shape Waterproof non-wicking Hypalon roll top closure In the base of our best-selling eVent Compression Dry Sacks, Evac Dry Sacks and Ultra-Sil Compression Dry Sacks. In this application, the laminate utilizes a 40 denier nylon face fabric: the material allows air to be pushed out of the dry sack/compression dry sack but prevents water from entering. This means you can compress the air out of a dry sack without needing a purge valve!. In the upper section of our Quagmire and Alpine Gaiters. In this application, the laminate utilizes a 70 denier nylon face fabric. The material allows perspiration to pass through easily but prevents external water from entering. The result: waterproof protection and superior breathability!