Closed-Cell Polyethylene Design: Durable, resilient closed-cell caulk saver foam with a water-resistant outer skin that helps resist punctures, moisture, and chemical exposure for long-lasting and reliable joint performance. This gap filler foam is highly flexible and easy to cut, yet highly resilient, ensuring an ideal fit in almost all spaces Ideal Depth Control for Sealants: This foam rod acts as a precise depth gauge, ensuring proper joint dimensions for optimal sealant adhesion and flexibility without requiring a bond breaker. Compatible with Most Sealants: This backing rod works well with urethane, silicone, acrylic, butyl, polysulfide, latex, and chinking sealants, making it a versatile foam filler for gaps and multiple construction and sealing applications. Wide Range of Applications: This wall crack filler is suitable for wood cracks, wall cracks, door or window joints, concrete expansion joint filler for sidewalks or driveways, glazing, curtain walls, isolation joints, and other common construction and sealing applications. Available in sizes ranging from 1/4-Inch to 5-Inch. Superior Performance: This backer rod 4 Inch diameter is chemically inert & stain-resistant, water-resistant, and able to withstand extreme temperatures from -90°F to 190°F, with >90% compression recovery for lasting shape retention in indoor and outdoor applications. This high-performance closed cell backer rope is designed to support clean, reliable joint preparation for sealing and glazing applications. Made from resilient polyethylene backer rope foam, it features a water-resistant outer skin that helps resist moisture and jobsite wear while providing consistent depth control for cold-applied sealants. The foam backer rope 4 Inch Diameter x 72 Inch Long, 1 Pack is ideal for larger gaps where stability and support are critical. This concrete backer rope is compatible with common sealants including silicone, urethane, acrylic, latex, butyl, polysulfide, and chinking propeucts. It is commonly used in expansion joint applications, glazing projects, log home chinking, curtain walls, coping joints, isolation joints, and parking decks. Contractors also rely on it as a dependable expansion joint filler for driveway sealing and other concrete joints where controlled sealant depth improves performance. Unlike open-cell materials, this poly foam caulk saver is chemically inert, stain-resistant, and engineered to withstand temperatures from -90°F to 190°F. With over 90% compression recovery, these durable foam ropes maintain shape after compression and help extend seal life. Flexible and lightweight, this backing rope for caulking installs quickly using a blunt tool or roller. It does not adhere to sealants, allowing proper curing and clean tooling. Available sizes include backer rope 1/4 inch, backer rope 3/4 inch, 1/2 inch, and also available in backer rope 1+ inch. Offers an efficient solution for filling deep gaps, including filling gaps between deck boards and use as a controlled concrete gap filler or foam crack filler support layer.