Before these were introduced, there were only two choices in competition rockers: Stainless steel for reliability, or aluminum for light weight and low cost. Now theres a third choice. Competition Cams Pro Magnums deliver the strength of chrome moly steel with less weight at the valve than aluminum. Made from 8650 chromemoly steel. This material is some three times stronger than 7075-T6 aluminum which is used on most aluminum rockers. So strong that Comp Cams will guarantee the rocker bodies for life against breakage.