M-D 71480 Foam Backer Rod, 1/2 In. Dia. X 20 Ft., Gray

The M-D 71480 Foam Backer Rod is a closed-cell polyethylene pre-caulking material designed to provide a solid backing for sealants and caulks on large gaps and openings. Used before applying caulk, this backer rod fills voids and creates a proper backing surface that allows sealants to cure evenly and bond correctly. By preventing three-point bonding—where sealant contacts three surfaces instead of two—the rod ensures better flexibility and longer-lasting, more durable seals on windows, doors, expansion joints, concrete cracks, and other construction applications.

This versatile gap filler is essential for both professional contractors and DIY enthusiasts who want reliable, weather-proof results. The non-absorbent, closed-cell construction repels moisture and resists water damage. Its compressible design adapts to irregular gaps of varying widths, making it suitable for interior and exterior projects where a professional finish is required.

Features and Benefits

• Closed-Cell Polyethylene Construction: Non-absorbent material repels moisture and resists water damage, ensuring the backing remains effective over time.
• 1/2 Inch Diameter: Fits standard caulk guns and matches common sealant widths for seamless integration into your project.
• 20-Foot Continuous Length: Reduces material changes and minimizes interruptions, saving time and money on large-scale applications.
• High Compressibility: Adapts to irregular gaps and varying surface contours, delivering uniform sealant depth and optimal adhesion.
• UV-Stable Formula: Maintains structural integrity under direct sunlight, suitable for both interior and exterior use.
• Prevents Three-Point Bonding: Creates proper two-point contact for sealant, allowing better movement and flexibility for longer-lasting joints.

Specifications

• Brand: M-D
• Model: 71480
• Material: Closed-cell polyethylene
• Diameter: 1/2 inch
• Length: 20 feet
• Color: Gray
• Use: Fill gaps and openings larger than 1/2 x 1/2 inch before caulking

How to Use

• Insert the foam backer rod into gaps and openings larger than 1/2 x 1/2 inch before applying caulk or sealant. The rod provides a backing surface that helps prevent three-point bonding and ensures proper sealant curing.