Exped VentAir Compression Medium Stuff Sack 100% waterproof and with 4 vertical compression straps to keep sleeping bags and other bulky items dry and compact. No purge valves required as the air is expelled through the yellow strip of VentAir fabric. The waterproof and breathable VentAir fabric enables easy compression through a 360 vapor permeable fabric strip. Volume: 19 L Waterproof performance and simple compression.