M-D Gray Polyethylene Caulk Backer Rod For Driveways and Sidewalks 20 ft. L X 1/2 in. T

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.
Non-absorbent, closed-cell polyethylene pre-caulking material
Easily trimmed to size with scissors
Twist multiple strands of cord together for extra large gaps