Performance Clutches - Performance Flywheel mm T (F-6078-L1)Technical Notes Engine Code 4G63T, 7 Bolt Crank Weight 5. 2Kg Manufactured from solid one piece billet or chromoly steel forging and specifically designed to reduce weight and inertia for better engine response. Unlike an aluminium or other multi piece design that is common in the market, the ring gear teeth are an integral part of the main casting, preventing any possibility of separation due to the different expansion coefficients of aluminium