EXEDY Racing Flywheels are made from solid one-piece billet chrome moly steel or chrome moly 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 to improve the cooling of the clutch. The ring gear teeth are milled onto the flywheel unlike an aluminum flywheel where the ring gear is pressed onto the flywheel which has the possibilities of separating from the flywheel. This could cause the flywheel to explode due to two different expansion coefficients (aluminum flywheel pressed on steel ring gear). EXEDY steel billet and forged steel flywheels have passed engineering tests to 15,000 rpm. They are guaranteed to be explosion proof at the said rpm.