Most fabrics are only as waterproof as their seams. For boat covers, awnings, rucksacks and other outdoor gear, Iosso’s Seam Sealer keeps moisture where it belongs—on the outside. It forms an effective, invisible seal against water intrusion without altering the color or feel of the material. It prevents leaks on cotton, cotton blend, polyester and synthetic coated fabrics. With the correct seam construction, it’s even effective on vinyl coated and vinyl laminate materials.