Just got these from AKG
Differential Mount Bushing Set, Poly 75D – Z4 (M)
Product Description
Differential Mount Bushing Set – U.S. Military Spec Polyurethane 75D
For BMW E46 M3, Z4M
Recommended for race use only
Set of three
Poly 75D race use.
Btw, I have to comment on the customer service at AKG, it's bloody FANTASTIC!!