All flywheels are light-weight aluminum models machined from T6-6160 Aluminum. They incorporate a replaceable steel contact surface and a steel outer ring gear for smooth starter engagement. All mounting hardware is Grade-8. The weights have been carefully chosen to maximize performance while maintaining maximum streetability. Benefits: Reduced mass equals increased acceleration. A lightweight flywheel works particularly well with turbo-charged engines because it reduces typical turbo lag. Increased supercharger efficiency due to less parasitic drag on the crank. Improved mid-range torque in a normally aspirated engine due to not having to overcome the heavy weight of a stock flywheel. CM uses only 6061-T6 aircraft grade or better billet aluminum in the manufacturer of its flywheels. CM uses High Carbon steel for the friction surface. (Replaceable) CM uses an OEM steel ring gear secured by bolts. CM offers a limited lifetime warranty. CM Billet Aluminum Flywheels meet SFI Spec 1.1 or 1.2 ------------------------------------------------------------ THIS ITEM CAN NOT BE RETURNED UNLESS THERE IS VERIFICATION BY THE CLUTCH MASTERS TECH (HELP) LINE. IF THERE IS ANY PROBLEM DURING INSTALLATION CALL THE TECH LINE FOR ASSISTANCE