Waterproof Material Backpack rain covers are typically crafted from waterproof materials such as nylon with a polyurethane (PU) coating or polyester laminated with a waterproof film. These materials are designed to repel water effectively, preventing it from seeping through and reaching the contents of the backpack. Even in heavy rain or wet conditions, they create a reliable barrier against moisture. Lightweight and Portable One of the key features of backpack rain covers is their lightweight nature. They are designed to add minimal extra weight to the backpack, making them ideal for travel, hiking, and other outdoor activities where every ounce counts. Additionally, they are highly portable, often able to be folded into a small, compact size that can easily fit into a pocket or a side - pocket of the backpack.