Ah sweet you can buy the two piece blank rotors from IAP too. I didn't actually realize the stock discs were 2 piece, currently I have 1 piece fronts, probably non genuine. I'd prefer blank discs vs the slotted/dimpled discs
BR900724:
http://www.ebay.com.au/itm/Disc-Brak...4AAOSw~gRVn~PZ
But looks like you can buy 2 piece genuine blanks from FCP euro anyway for a similar price:
https://www.fcpeuro.com/products/bmw...5i-34116778647