eVent Sil Drysacks are ultralight waterproof roll closure bulk reducing sacks that are ideally shaped for easy and efficient packing. The extremely waterproof breathable eVent bottom allows air to escape as the sack is roll compressed, yet maintains its wonderful block shape that is ideal for stacking in your pack. Granite Gear also added an arched rolling stay that helps keep the top of the sack open while loading and shapes an easy to grab handle when sealed. The ultimate cure for compression. Reduce weight and bulk! Not intended for submersion.