Description of Outdoor Research Helium Compression Sack #1 This lightweight compression sack reduces sleeping bags and other stuffables to a pack-friendly size. The silnyl fabric resists moisture and slides into your pack with ease. A pocket in the end cap keeps track of small items. Features: Dimensions: 17 5/8" x 6" (45 x 15cm) Volume: 498cu.in. (8.2liters) Average Weight: 3.6oz (102g)