There are two components to the M Perf Suspension:
1. Suspension Kit - struts/bump stops/etc: $1500 or so.
2. Spring Kit - $500 or so.
You need both, as I learned the hard way...
2012 335i Mineral Gray
Enzo 400R+|M Performance Exhaust/Brakes/Suspension/LSD|Bav Stage 1/AMP||ER CP/IC/DP | Dinan CAI/N55 PWG BIG TURBO|BMWF30.com