It allows you to shorten the panhard bar so that the rear end is centered (and your driver wheel doesn't stick out further than the passenger wheel).
Due to the geometry of the panhard bar, when you lower the vehicle, it pushes the driver side wheel out. How much it pushes it out just depends on how far off center you were from the factory and how large of a drop you choose.
08 Mustang Gt automatic.
I have the eibach sportline springs and The Prodamper struts on it and they run really smooth !!! worth it ! The front drop was 2 inches and the back was 1.75.
and on the CAI I have a Diablo Sport Tuner and the C&L cai and I got around 40-45 Hp Gains ! Daily Driver too.