When you need to compress volume without significantly adding weight, the Ultra-Sil Compression Sack is an excellent solution. Made from a 30D diamond rip-stop siliconized Cordura fabric they can be compressed to one third of the original volume. Ideal for use inside your pack or travel bag when you need to compress clothing or bulky soft items to allow space for other essentials or fun holiday items. In a perfect world, with perfect contents, this compresses down to 1/3rd its original volume (i.e. from 15 to 5 liters). Note: seams are not tape-sealed; therefore this product is not waterproof - only water resistant