Review on Frelaxy Upgraded Waterproof Backpack Rain Cover: Triple Waterproofing, Anti-slip Cross Buckle Strap, Ultralight & Compact Portable, Ideal for Hiking, Camping, Biking, Outdoor Adventures, and Traveling by Melvin Boss

Unfortunately that's bad design. Yes, it will keep your pack completely dry. Before. Water pools on the bottom, eventually leaving over 5 pounds of water on the bottom. The straps help keep it wrapped around the backpack. There is no drain at the bottom of the liner. So if water runs down your back during a rainstorm, it collects INSIDE the rain cover and has nowhere to go. Leave your pack and gear soaked unless you have a separate liner. It will be great if you add some drainage. In addition, the material is thin. If your backpack is placed on a rocky surface or something hits it, it will tear easily.