Competition Cams Pro Magnum roller rocker arms combine the strength of 8650 chromemoly steel and the weight savings of aluminum rockers. Comp Cams took advantage of computer design to simulate the stresses that affect the rocker under various operating loads. This allowed the engineers to lessen the rockers' mass at non-critical areas and strengthen the areas that take the most punishment. The results: Rocker arms that are strong where they need to be, and actually weigh 5 percent less at the valve than comparable aluminum rockers. (Set of 16)