Ralco RZ Lightweight Chromoly Flywheels are made from 4140 one-piece billet chromoly steel. 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 possibility of separating from the flywheel. All Ralco RZ Chromoly flywheels have passed engineering tests to 12,000 rpm.