Manganese bronze. Comes with special shoulder for ease of installation. Takes OEM valve seals. Shortened to accept valve lifts up to .600". Softer and less durable then C630 bearing bronze but will allow a lower cost and reaming to size is quick and easy. Finish can be done with simple tools like a ball hone and an electric drill. Rapid heat transfer and excellent lubricity. Note: Special Manganese reamers & hones are available. 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).

Manganese bronze. Comes with special shoulder for ease of installation. Takes OEM valve seals. Shortened to accept valve lifts up to .600". Softer and less durable then C630 bearing bronze but will allow a lower cost and reaming to size is quick and easy. Finish can be done with simple tools like a ball hone and an electric drill. Rapid heat transfer and excellent lubricity. Note: Special Manganese reamers & hones are available. 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).

Manganese bronze. Softer and less durable then C630 bearing bronze but will allow a lower cost and reaming to size is quick and easy. Finish can be done with simple tools like a ball hone and an electric drill. Rapid heat transfer and excellent lubricity. Note: Special Manganese reamers & hones are available. Note: Standard non-oversize dimensions (for reference only) are 0.5620" O.D. (14.27mm); 0.2750" I.D. (6.99mm); 2.02" OAL (51.31mm).

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 0.4750" O.D. (12.07mm); 0.2342" I.D. (5.95mm); 1.655" OAL (42.04mm).

Cast Iron offers maximum durability and wear resistance for long distance touring. The standard since the invention of the piston engine. Note: Standard non-oversize dimensions (for reference only) are 0.4750" O.D. (12.07mm); 0.2342" I.D. (5.95mm); 1.655" OAL (42.04mm).

Manganese bronze is softer and less durable then C630 bearing bronze but will allow a lower cost and reaming to size is quick and easy and finish can be done with simple tools like a ball hone and an electric drill. Rapid heat transfer and good lubricity. Note: Special Manganese reamers & hones are available. Note: Standard non-oversize dimensions (for reference only) are 0.4750" O.D. (12.07mm); 0.2342" I.D. (5.95mm); 1.655" OAL (42.04mm).