I have set of rear springs for a E90/E91. These are same springs also found on the M3 KW kits, though only on KW v3s.
KW Part number is 2017 (60210152) which denotes to be a 630lb/In spring. KW street comfort, V1 and V2 come with 2012 which is a 570Ib/In spring. So these are an upgrade for those wanting a firmer spring in the rear, they are a direct replacement, ideal for anyone who wishes to track there car or simply increase performance characteristics of there suspension.
Total price shipped is £130.00 for the pair.
As you can see I got these directly from KW Germany. They are 100% genuine and brand new unused.
Any questions please let me know.