The OEM hitch sticks out slightly from the regular bumper. It is more visible with the aero bumper (a recent post showed a cover over the hitch on that bumper - I didn't like the look, but that is me).

I don't mind the look of the hitch, and there is no trimming required with the OEM hitch. With the aftermarket hitches, some have had to trim the bumper material slightly. I don't think there would be room to have a receiver behind the standard hitch cover, but it may be possible to trim the cover, and reinstall it with only the 2" square receiver showing - I saw a post with that done once.

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue