ACTION Lightweight Flywheels for the K Series engines have three major benefits: low weight, low inertia and high thermal capacity. They are specifically made for light to high tuned racing cars that see drag racing, autocross, street use, and rally events. They are made from a durable one-piece billet chromoly steel or chromoly steel forgings. Action specifically designed this flywheel for reduce in weight and inertia for better engine response. We have tested our lightweight flywheels and they have passed engineering tests up to 15,000-18,000 RPM. They are made to not to fail to the provided RPM's. With a heat-treated friction and integrated ring gear, Chromoly Flywheels are an excellent choice for any performance build.