Kool-Rod is a closed cell, polyethylene, flexible, rope-like foam joint backing material. This material is virtually non-absorbent and chemically inert to most solvents. It will not stain or adhere to sealant materials. It is fully compatible with polysulfide, silicone, acrylic, butyl, polyurethane, and most other cold-applied sealant compounds. Kool-Rod is specifically designed as a compressible backing material to be used in conjunction with a wide variety of cold-applied joint sealants.