In the age of ultra-lightweight everything, Sea to Summit has developed a range of ultra-lightweight dry sacks to save those crucial few grams. Using a 15 denier Sil/PU nylon fabric it calls Ultra-Sil Nano, a lightweight side release buckle and a thinner roll top closure, Sea to Summit created a dry sack that is 30% lighter than its standard 30 D Ultra-Sil Dry Sacks!