Sea to Summit Ultra-SIL Stuff Sack Made of 30D Diamond Siliconized Cordura The fabric is impregnated with silicone to make it waterproof to a hydrostatic head of 2000mm Fabric has a slippery finish for easy packing Reinforced pull handle on bottom Uses the smallest possible cord and cord lock for top closure water-resistant products (such as the Ultra-Sil Stuff Sacks) are siliconized on both sides for ultimate packability waterproof products (such as the UltraSil Dry Sack are) siliconized on the outside and PU-coated on the inside to allow seam taping.