Proflow's Shaftmount roller rocker arms are crafted from certified aircraft-6061, heat-treated aluminum. They are then matched to massive, precision-ground trunnions for superior durability. These ocker arm geometry is optimized to evenly distribute loads for maximum strength. Proflow's roller rocker arms are available in several sizes, ratios, and mounting styles. Features include: * Oversized needle roller bearings for better load distribution and longer service life * Black anodized for a great appearance * Extruded bodies have a tensile strength of over 60,000 psi * Stud-mount rockers can withstand valve spring loads up to 360 lbs. * Pedestal-mount rockers can withstand valve spring loads up to 600 lbs. * Shaft-mount rockers can withstand valve spring loads up to 700 lbs.