HERCULES URETHANE BACKUP Ring 90A DUROMETER

Urethane at 90A durometer sits on the firmer end of the scale for backup rings. Stock seals often run softer, so swapping in a 90A urethane piece gives you better resistance to extrusion under pressure. For most hydraulic cylinder applications where fluid wants to push the primary seal out of its groove, that extra firmness is exactly what keeps the assembly holding together over time.