Made in the USA
Softer Manganese guides are easily reamed, and then can be delicately finished with Kibblewhite high quality ball hones
Expect the same exacting KPMI® tolerances, but with a reduced toughness / wear-ability when compared to premium C630 Nickel Aluminum Bronze valve guides
With any battery operated or electric drill you can ream and hone manganese valve guides in less time