The Whiteline Rear Differential Positive Power Kit Inserts are inserts to the rear differential bushings.  These are not factory replacement bushings, these are designed to fill in the voids of the factory bushings so you don’t have to press the factory bushings out. The job of the Whiteline Rear Diff Positive Power Kit is to secure the rear diff in its cradle within the subframe.
Your rear differential will have substantial movement or flex under hard launches, as well as hard acceleration. After installing these Whiteline inserts, the movement will be significantly reduced, and this will improve cornering, and improve launches, and overall improve the feel and dynamics of the car.¬â€