Forever ends the debate about whether you can afford the extra weight of a pack cover - the medium size weighs only 4 ounces and packs into a tiny stuff sack. Made of 30D Diamond Ripstop silicone impregnated Cordura, so its waterproof finish can't peel or wear off over time Siliconized Cordura® is about one third the weight of traditional coated nylon This pack cover uses a "no seam" construction for complete waterproofness Has a mid-back keeper strap that helps secure it to the pack and keep the sides from catching wind Comes packaged in its own mini siliconized nylon stuff sack that remains attached to the cover so it can't get lost