The Enthuspec solid bushings for the S13 Nissan 240sx allows you to use a S14, J30, Z32 NA, S15, and Skyline rear differentials while still using your factory S13 aluminum cover. Intended to use for S13 Subframes. These can also be used on S14 Differentials in an S14 subframe but can still use the OEM Bolts. The OEM Factory bushing used in the subframe is very soft and flexible. The differential moves alot under hard accelerations and driving conditions. Most of that flex is pivoted off the driveshaft rear yoke, thus making the front of the differential to dip down and twist. These bushings solidly hold the differential to the subframe, eliminating the unwanted movement and help with wheel hop to get the power to the ground. Bushings are CNC machinced aluminum for precision fitment. Designed for racing purposes where noise and vibration is a trade off for performance.