1/2″ X 1/2″ X 20′ Gray Closed Cell Poly Foam Backer Rod

Before caulking, use the MD Building Products 1/2 in. x 20 ft. Caulk Backer Rod to help fill gaps and openings in pavement cracks, wall joints, foundations, sidewalks and driveways. The backer rod helps cushion and insulate and helps prevent 3-point bonding.