These fabrics usually Use a durable water repellant (DWR) end applied to them, which happens to be most frequently a hydrophobic coating that resists rain and prolongs soaking your backpack but can even be a polyurethane coating as in the case with the Patagonia Black Hole Backpack, or maybe a https://single-cruise62481.blogsidea.com/33852927/a-simple-key-for-bird-backpack-copyright-unveiled