REI Duck's Back Rain Cover - 100 Liters - $13.83

With a waterproof polyurethane coating to keep out the rain, the REI Duck's Back 100 backpack cover lets the elements roll off your pack even if you're not a duck. Drawstring shockcord with toggle lock securely cinches around pack for a snug fit. Reinforced bottom prevents damage when setting pack on rough surfaces. Zippered storage pouch doubles as an accessory pocket to stash small essentials; offers a vertical strap for easy securing or belt clip for quick horizontal attachment. Cover has bottom drain hole for release of trapped moisture. Pouch dimensions: 6.75 x 4.75 x 2.5 in. - $13.83