It is an E46 M3 trunk spoiler, custom cut and sanded to fit the X5 roof
And it fits Perfectly!

Know anyone looking for This REMUS Exhaust?
It looks amazing ,like 4 Big chrome Gun Barrels shooting out the back
And the sound is truly Racecar like, under hard throttle or when downshifting in manual mode the sound is Exotic .
I loved it....