C630 bearing bronze. Comes with special shoulder for ease of installation. Takes OEM valve seals. Shortened to accept valve lifts up to .600″. 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 0.5620″ O.D. (14.27mm); .3085″ I.D. (7.84mm); 2.100″ OAL (53.34mm).
