Pair of EIBACH 12MM WHEEL SPACERS and 10 Extended Wheel Bolts SET for BMW F30 F32 E60 F10 F8X M3 M4 etc.
Total track Widening: 30mm
15mm spacers x 2
Extended bolts x 10
Q: What size spacer should I use?
A: General rule is to measure the distance between your tyre wall to the inner wheel arch and see how much you could push the wheel/tyre out by. The wheel/tyre should not be extended further than wheel arch for legality reasons.
Always check your bolt tightness from time to time, especially after track day use.