Sea to Summit Ultra-Sil Pack Cover-Medium-Lime Green. It's a tiny and compelling solution and the medium size weighs less a mere 4 ounces. Packs into its own small stuff sack - why wouldn't you carry one? Features of Sea to Summit Ultra-Sil Pack Cover Made of 30D Ultra-Sil fabric constructed from CORDURA yarns for durable waterproof performance. This pack cover does not use seam construction to ensure that it is completely waterproof Packaged in its own mini siliconized Nylon stuff sack that remains attached to the cover so it can't get lost Keeper strap (sizes S-L) pulls the pack cover tight across the pack harness Sold in four sizes to fit daypacks up to large backpacks Size Guide X-Small:Fits a15 to 30-liter pack Small:Fits a30to 50-liter pack Medium:Fits a50to 70-liter pack Large:Fits a70 to95-liter pack Pro Tip:Ifyou stow any gear externally on your pack we would recommend buying an Ultra-Sil Pack Cover a size larger than normal. Package Contents: Sea to Summit Ultra-Sil Pack Cover Sea to Summit Ultra-Sil Pack Cover-Medium-Lime Green