EXEDY Racing Flywheels are made from solid one-piece billet chromoly steel or chromoly steel forgings. They are specifically designed to reduce weight and inertia for better engine response. Most incorporate special design features to enhance the air flow that cools down your clutch. The ring gear teeth are milled onto the flywheel unlike an aluminum flywheel where the ring gear is pressed onto the flywheel and have the possibilities of seperation. All flywheels have passed rigorous testing standards in which they are tested to 15,000 rpm without problem.