Backer rod does not stain sealants and is chemically inert. They are non-gassing, non-exuding, and virtually dust-free. Due to physical and chemical inert nature, backer rod is compatible with virtually all known cold sealants, including self-leveling sealants - butyl, polysulfide, acrylic polyurethane, silicone, and most other cold-applied sealants.
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