CRL Closed Cell Backer Rod is a round, flexible, closed cell polyethylene foam with an exterior "skin" used as a backing and thickness control device for elastomeric and other cold-applied sealants. The Backer Rod becomes an integral part of the joint into which it is installed, and therefore is available in a range of diameters to accommodate joints from 3/16" to 1-5/8" (5 to 41 mm). It limits the depth of the sealant, thereby preventing excessive use of the sealant, which promotes proper joint design. Because the sealant will not bond to the "skin" of the rod, it can stretch and recover with joint movement, with minimal stress being put on the points of adhesion to the substrate. CRL Closed Cell Backer Rod will not absorb water or wick water to joint walls, which could cause adhesive failure. It is compatible with cold-applied sealants, and its round shape promotes the preferred "hourglass" shape for joint sealants. It withstands hot and cold temperature extremes from -45° to 160°F (-43° to 71°C). CRL Closed Cell Backer Rod is chemically inert, and resistant to oils, gasoline, and solvents. It will not stain or "bleed" into sealant material. Backer Rod is typically used in expansion/control joints where cold-applied sealants are used. These joints would normally be found in curtain walls, construction partitions, precast panels, parking decks, door and window frame perimeters, coping, floor and deck joints, horizontal traffic joints, and building rehabilitation projects.