At only 4.5 ounces, the Osprey UL Raincover (Large) takes up very little space in your backpack yet comes up big when bad weather strikes. Taking a few moments to place this fully seam taped fly on your pack when the first drops fall is much better than spending a whole day post-storm spreading your gear out on rocks waiting for everything to dry out. On cold, clear nights, the UL Raincover (Large) also does a great job of keeping dew and frost off your backpack. Fabric: 40 denier silnylon (silicon impregnated ripstop nylon). Fully seam taped. Drawstring closure with toggle tightener for a secure fit. Built in storage bag. Fits packs 3600 cubic inches (20-40 l) and up. Weight: 4.5 oz. (0.13 kg.).