Forged from 8620 steel for greater strength. S&S roller rockers are stronger and designed to combat excessive valve thrust and valvetrain wear with higher lifts from .550" and up to a maximum of .650" valve lift. The rocker geometry is better suited for higher lift cams and the 50% longer shaft bushings to help increase valvetrain lif. Larger surface area on the thrust surfaces reduces wear on the heads and oil is sprayed directly on the valve springs for better cooling to help avoid broken valves due to excessive heat. Comes with standard 1.640 M8 rocker ratio. Note: See 597872 for a complete rocker arm rebuild kit with all components that are required.