Made of siliconized Cordura, Ultra-Sil dry sacks are 50% lighter than standard dry bags of the same size. These bags are ideal for backpackers, who need to keep their gear organized and dry. The featherweight fabric is not recommended for kayakers and canoeists. Made of polyurethane-coated siliconized Cordura nylon for ultimate waterproofing. Nonwicking Hypalon roll-top closure with stiffener at the top for a better seal. Nearly transparent for good visibility of contents. All seams are double stitched and tape sealed. Uses nonbulky low-profile buckles. Soft and flexible with a slippery finish for easy packing. Round bottom.