EXEDY flywheels combine low weight, low inertia and high thermal capacity. They are designed for lightly tuned cars for drag racing, autocross, and rally events, as well as street usage. They 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 airflow which improves the cooling of the clutch. The ring gear teeth are integrated onto the flywheel unlike an aluminum flywheel where the ring gear is pressed onto the flywheel and has the possibility of separating from the flywheel due to the different expansion coefficients of aluminum versus steel. EXEDY steel billet and forged steel flywheels have passed engineering tests to 15,000-18,000 rpm. They are guaranteed not to fail to the said rpm, and are all SFI approved.