Sea to Summit eVAC Dry Sack. The new eVAC Dry Sack is a slimmed down version of Sea to Summit's award winning eVENT Compression Dry Sack. It uses waterproof, air permeable eVENT fabric on the base for valve free air expelling, allowing compact packing. Instead of straps for compression, you just roll the sack down and air is pushed out of the base. Then close the buckle and you've just saved space and weight. The sack is oval shaped, rather than round, so they resist rolling when laid on their side. Suitable to keep contents dry in any wet situation where the bag is not submerged.