Permobond® RS-3508 Triply Series specially designed for chemical service, abrasion and chlorinated gas service with low water absorption. Built with a soft Natural ply followed by a semi-hard center for maximum permeation resistance and a flexible soft natural ply for best rubber to metal bonding. The third ply’s flexibility permits expansion and contracting with thermal variations of the metal substrate. Often used in applications such as Phosphoric Acid for it’s low permeation physical properties.