Kibblewhite Precision KPMI GUIDE, C630, EX STD, 30-33530 fits 1972-1977 Honda CB350F / CB400F

C630 Bronze: We choose to use the copper based C63000 nickel-aluminum bronze as a material to make our bronze valve guides because of its idealcharacteristics for the application. The 5% nickel content provides superior resistance to wear, and the approximately 80 percent copper content delivers outstanding heat conductivity. KPMI® guide profiles are designed to have minimal effect on the airstream while maintaining critical cross sectional thickness in high temperature areas, which promotes high performance and endurance.Manganese Bronze: These Engine Builder valve guides have been designed with the price conscious builder in mind. Expect the same exacting KPMI® tolerances, but with a reduced toughness / wear-ability when compared to premium C630 Nickel Aluminum Bronze valve guides. The softer Manganese guides are easily reamed, and then can be delicately finished with our high quality ball hones. Now, with any battery operated or electric drill you can ream and hone manganese valve guides in less time and in the absence of expensive honing equipment required to properly size tough Nickel Bronze guides.