M-D Building Products 5/8 in. x 20 ft. Caulk Backer Rod

The M-D Building Products 5/8 in. x 20 ft. Caulk Backer Rod is a non-absorbent, closed-cell polyethylene foam cord designed to fill large gaps and joints before applying caulk or sealant. By filling openings, it prevents three-point bonding and ensures caulk adheres only to the intended surfaces for a flexible, long-lasting seal. This pre-caulking filler insulates, cushions, and seals against drafts and moisture infiltration. It can be easily trimmed to size with scissors or twisted together for extra-large openings, helping to save caulk and improve overall sealing efficiency in both indoor and outdoor applications.