It was the success of Sea to Summit's Compression Dry Sacks that prompted the creation of a lightweight version. It boasts the same clever functionality as the original Compression Dry Sack - by using air permeable eVent fabric that allows air to be pushed out of the sack, without allowing water in. It's now ultra-light - compressing gear to one-third of it's volume while keeping it dry. Air passes out through eVent fabric for efficient compression. Made from Ultra-Sil 30D siliconised high-tenacity Cordura tylon fabric with exceptional strength. Waterproof seams, double stitched and fully tape sealed. Waterproof and air-permeable eVent fabric base. Hypalon closure does not wick moisture. Reinforced stitching on all stress points. Air compresses out, water can't get in. Roughly half the weight of the original Compression Dry Sack.