Sea to summit ultra sil nano dry sack blue 20l in the age of ultra lightweight everything we have developed a range of ultra lightweight dry sacks to save those crucial few grams here and there using a 15 denier silpu nylon fabric we call ultra sil nano a lightweight 16mm side release buckle and a thinner roll top closure we have created a dry sack 30 lighter than our standard 30 denier ultra sil dry sacks ultra sil nano tm 15 denier nylon fabric for advanced strength to weight perfo