The M-D Caulk Backer Rod is a 3/8 in. diameter x 20 ft. length foam rod used to fill gaps and joints before caulking.

• Made from closed-cell, nonabsorbent polyethylene foam
• Gray color for a neutral, professional appearance
• Fills large gaps and joints larger than 1/2 in. to reduce caulk usage and improve bead shape
• Suitable for use around windows, doors, and other openings to block drafts and moisture
• Works for both indoor and outdoor caulking applications