Molded from 93 Shore A polyurethane with a 70 Shore A energizer, this seal utilizes the same groove dimensions as a standard o-ring to T-seal. One or two Style 575 back-up rings may be used for wider grooves. Extrusion resistant by design, this seal also is resistant to rolling and twisting. Installation is an easy two step snap-in procedure with no need to re-size before insertion into the bore. NOTE: Piston diameter 'I' dimensions are given for pistons without wear rings.