The Eibach Springs are great quality springs. Everyone I ever knew that used the Eibach Springs to lower their Ford Mustang was quite happy with them. The Eibach Pro Kit Springs make for the perfect drop and stance I think. The only problem I ever heard about Eibach Springs are the Eibach Sportline Springs sag over time. I am not sure if Eibach corrected the problem with the Sportline Springs or not don't quote me on it. I would do it right the first time though and install new struts and shocks and quad shocks, caster camber plates, and go to the dealership or whatever shop you go to and to get an alignment after your new springs are installed. I had a bad alignment before unevenly wear both my front tires. An alignment is well worth the investment as it will save your tires over time.