These Black Venom series rollor rocker arms are CNC machined from aircraft grade aluminum and come with needle bearings and hardened roller tips and shafts. The product is dyno tested at 10,500 RPM and proven to provide more horsepower. They show a 3% increase in maximum torque and horsepower over standard aluminum rockers. These roller rocker arms work with the Honda GX200, Clone englines, and Predator non-hemi engines. It will not work with hemi Predators or the Ducar 212 engine.