I've never had eibach lowering springs for the X5. But I have used them for my M3 and they are great. IMO much better then H&R in quality. I have been to the eibach factory and know for sure the quality control is better then that of H&R. In addition, H&R doesn't have an in-house development program here where eibach does. But don't get me wrong. H&R are still good springs over all. I just feel eibach are better from my experience.

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Lemans Blue X5 4.8is
Dynaudio
Diamond TDX 12" subs x 2
Xtant X604 x 2
Xtant X1001 x 1
VST 7" LCD x 2