SPEC billet flywheels are manufactured and developed for specific driving environments and recommended based on how each car reacts to changes in rotating mass. SPEC flywheels are NOT a one-fits-all lightweight flywheel, though they can be used for an array of driving habits and racing/high performance applications. Consult a SPEC representative for a recommendation. Manufactured from only the highest quality steel and aluminum, they are the only flywheels on the market manufactured to a .001 machine tolerance, guaranteeing a flat seating surface for the clutch and smooth rotational qualities for perfect balance and extended engine life. Aluminum Flywheels are generally half the weight of stock steel flywheels. Aluminum Flywheels provide faster revving, less drag on the engine, and quicker response then heavier Steel Flywheels. Steel Flywheels tend to be a little easier to drive on the street due to the fact they lose less RPMS will shifting. Aluminum Flywheels also feature a replaceable steel friciton plate.