I have the BMW Performance carbon fiber front splitters replica from China eBay seller 4AMotors and believe me they are the same as OEM. I have a buddy who bought a set OEM and we compare, they fit and look the same.
So if I where to buy this rear diffuser I would buy it from 4AMotor. Have received 2 set of splitters and they have been flawless.
By far this is the best rear diffuser I have seen so far for our M3. This would be a great Christmas present.