SuperPro's rear differential center support bushing drastically reduces the deflection of the OEM rubber differential mount under changing loads - especially rolling on and off the throttle. This offers benefits in throttle response and in manipulating the cars cornering attitude with the throttle as the car will react more quickly and directly to changes in throttle input. In addition the SPF3404-80K offers a vastly extended service life over the soft rubber OEM piece backed by a lifetime warranty. As the higher durometer version of this kit the SPF3404-80K sharpens responses over the standard version but will come with a small increase in NVH due to the higher durometer material Looking for a more daily driver or street car-friendly version? See our SPF3404-70K; the lower durometer version of the rear center differential mount.