This M-D backer rod fills gaps and joints before caulking to create a professional, long-lasting seal. Made from non-absorbent, closed-cell polyethylene, the rod acts as a bond breaker to prevent 3-point bonding -- ensuring caulk adheres only to the two joint faces for maximum flexibility and durability.

• 1/2" diameter x 20 ft length
• Closed-cell polyethylene -- non-absorbent and moisture resistant
• Ideal for medium gaps approximately 3/8" wide
• Prevents 3-point bonding for longer-lasting caulk joints
• Use in expansion joints, pavement cracks, window and door gaps
• Suitable for indoor and outdoor applications
• Easily trimmed to length with scissors

Tip: Select a backer rod approximately 1/8" larger than the gap width for a snug friction fit. Push rod into the joint, then apply caulk or sealant on top.

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