KOSTER IN 7 is an elastic polyurethane prepolymer used with 10 % catalyst. The product reacts only when coming into contact with water and forms a compact, viscoplastic, waterproof polyurethane foam. KOSTER IN 7 remains viscoplastic after reacting and is able to follow crack movements and seal permanently without the need for follow-up injections with an elastic polyurethane resin. KOSTER IN 7 is solvent-free and resistant to hydrolysis.