If you order RS pack springs from Ford you actually get Eibachs, going back a few years the Ford upgrade springs were blue and carried both the RS and Eibach logos, if you fit those to a new Ford it does not invalidate the warranty.........speel over. Eibachs are some of the best springs made a big proportion of competition coilovers use them, their road springs give a stiffer, lower but still not bone jarring, filling removing ride quality. Well worth a pop.