Gun grade, thick polyurethane recommended for sealing and caulking applications, particularly in movable joints and exterior environments.LOCTITE UR 7001 is a gray, gun grade, thick polyurethane recommended for sealing and caulking applications, particularly in movable joints and exterior environments. It cures to a flexible rubber that forms strong bonds to various substrates. When cured is has excellent adhesion, cohesion and elasticity and resists deterioration from weather, stress, movement, water and many chemicals.