what exactly do you have on your roof? something custom? it looks like it cleanly attaches to the bmw roof rack...
edit: this looks like the one you got.. seems to be quality..
http://www.ebay.com/itm/ROOF-RACK-CA...074#vi-content
__________________
2007 328xi Wagon, Black Sapphire Metallic, Sports Package, Cold Weather Package, Rear PDC, Airlift kit with 3P mgmt, CF Akrym rep lip, LCI M-Tech front bumper, LUX Angel Eyes, Black Kidneys, LED Interior Lights, M3 Steering Wheel with Extended Billet DCT Paddles, 19" Staggered VMR 710's