The Seal Ring 86712403 provides auxiliary sealing for the cylinder-piston gap in HC25 Hydraulic Rock Drills, working with primary seals to eliminate leakage. Generic seal rings use soft materials that wear within 800-1000 hours, reducing sealing efficiency. This OEM ring is made from wear-resistant alloy steel (HRC 45-50) with a polished surface that minimizes friction against the piston. It enhances the primary seal’s performance by 30%, preventing oil leakage even as primary seals near the end of their life, and requires replacement only when worn.