I am doing waterproof bags, generally this bag all use high-frequency hot pressing process, TPU coating is also divided into polyether polyester, and the simplest difference of PVC is that the main bag body does not involve sewing technology, then basically waterproof, why is it basically waterproof, because the zipper can not achieve the theoretical 100% waterproof, the current market waterproof best is Tzip zipper, with this zipper waterproof backpack is currently the most waterproof in the market, except for the roll design bag.