Keep your compressible gear dry- air squeezes out, water can't get in. The Evac Dry Bag is a bluesign-approved recycled 70D nylon waterproof main body fabric and a 70D eVent® waterproof but air-permeable base that allows you to push air out while still keeping your contents dry inside, resulting in more efficient space utilization. DWR finishes on both fabrics are C0 non-PFC. Pack your compressible items- sleeping bags and insulated clothing into the Evac Dry Bag, roll the roll-top closure down, then squeeze the bag to push the air out. This function allows you to fit items into your pack or travel bag more effectively. It was also designed with an oval base making them perfect for sliding into the contours of your pack. All seams are double stitched and tape-sealed. Pro-tip: sitting on a packed Evac Dry Bag is the best way to squeeze the air out- then pack the dry bag into a tight space in your bag or pack so it does not draw itself full of air again.