Willseal® 600 & 600S is a pre-compressed, self-expanding foam joint sealant, engineered to perform as a highly flexible, weathertight, primary or secondary seal in vertical exterior applications. (600 for primary or secondary; 600S in secondary only).

600S is specifically designed to provide the ideal foundation for a large variety of wet sealants, such as silicone, polyurethane, polysulfide, and acrylic. Unlike conventional wet sealant and backer rod methods, Willseal 600 & 600S is not susceptible to breakdowns caused by excessive or rapid joint movements, thus protecting structures against rain, wind, dust, and sound. Willseal 600 & 600S is waterproof to a wind-driven rain at 12.5psf (70mph) yet it is vapor permeable, making an optimal addition to any air barrier system, cavity wall joint, and interior partition application.