Willseal® Backer Roll is a pre-compressed, self-expanding foam joint seal, engineered to perform as a highly flexible, secondary seal in vertical applications. Willseal Backer Roll 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 Backer Roll is not susceptible to breakdowns caused by excessive or rapid joint movements, thus protecting structures against rain, wind, dust, and sound.