This O-ring seals a connection point within the hydraulic system of the host vehicle. It sits between two mating surfaces in the fluid circuit, preventing pressurized oil from leaking past the joint. A degraded or nicked O-ring will cause a visible external leak or a gradual loss of system pressure, reducing implement response time. The seal is manufactured to the original cross-section and durometer, which matches the groove geometry of the housing it was designed for. On reinstallation, ensure the sealing surfaces are clean and free of burrs, and lubricate the O-ring lightly with hydraulic fluid before assembly.