The osprey ultralight raincover is made from a waterproof fabric that protects the contents your bag from the elements when that rainstorm yoursquove been dodging all day has caught up yoursquoll need to quickly ensure your pack and gear is completely protected osprey have been continually developing their range of raincovers and have designed a range of ultralight raincovers perfect for defending against downpours the ultralight raincover packs down to roughly the size of a tennis ball