Whether fabric is stretched from wind or body movement, seams bear the brunt of the stress. Needle holes enlarge and sewn material pulls away to leave paths for water to seep through. Seam Sealer coats these areas with an invisible non-silicone waterproof barrier that doesn’t change the fabric’s feel, flexibility or color. Works equally well on both natural fabrics like duck cotton and synthetics such as acrylic and polyester. Depending on the construction, it can even work with vinyl and vinyl laminates. Made in the USA.