Willseal® 150 is a pre-compressed, self-expanding polyurethane foam joint seal, engineered to perform as a highly flexible, weather-tight, primary seal in vertical exterior applications. The high-density polyurethane foam is impregnated with a modified flame retardant, hydrophobic, UV stable acrylic resin and treated with a pressure-sensitive adhesive (PSA) on one side for ease of installation. Willseal 150 self-expands to fill the joint creating a permanent, elastic, vapor-permeable weathertight seal.