The Ground Control E36/Z3 Roll Center Adjusters replace the factory front lower ball joints. These new bushings assist in correcting the vehicles roll center after lowering. They are adjustable depending on your vehicles final ride height. We recommend using these bushings in conjunction with our Racing Tie Rods/Bump Steer Adjusters, to achieve proper suspension alignment. Our exclusive racing tie rod ends allow the bumpsteer to be adjusted, by moving the tie rods up and down with spacers. This is similar to the pieces used by BMW factory teams in Europe, and they recommend that the rod ends be inspected every session, and replaced if necessary. Our Kit comes with Aurora Aircraft grade rod ends and all spacers.