C630 bearing bronze is a tough nickel-aluminum-bronze alloy typically used in high performance and racing applications where rapid heat transfer from the valve to head is important. Note: Standard non-oversize dimensions (for reference only) are 0.5650″ O.D. (14.35mm); 0.3760″ I.D. (9.55mm); 1.880″ OAL (47.75mm).
