Built with tough 840-denier nylon tarpaulin fabric coated with thermoplastic polyurethane (TPU), water simply cannot penetrate it. The advantages of using a nylon fabric with this coating rather than polyester or canvas are lightness of weight, flexibility and abrasion resistance. The highly-flexible TPU coating is resistant to ultraviolet light and chemicals, ensuring durability and longevity without breakdown from hard use. The seams are radio-frequency (RF) welded, a cement-free process that permanently fuses the fabric layers together, assuring flexible integrity without fail. All webbing and padding is securely stitched to an additional layer of the waterproof fabric, which is then RF-welded to the bag’s body. This is the same construction as used in the manufacture of white-water rafting gear, where equipment failure could have fatal consequences.