The O’ring 86732526 seals the interface between the retainer socket and bearings in HC25 Hydraulic Rock Drills, a critical location for preventing oil contamination of bearings. Generic O-rings used in this position often harden within 500-600 hours, losing their sealing ability and exposing bearings to oil and dust. This OEM O’ring uses a high-elasticity rubber compound that maintains ≥85% elasticity retention over 800 hours, even in contact with hydraulic oil. Its precise dimensional tolerance (±0.002mm) ensures it fits the retainer socket’s seal groove perfectly, keeping bearings clean and lubricated until mandatory replacement.