OE tow hitches are reportedly in short supply for the E53. This has happened before, the kit is made for BMW by a third party. Just something to keep in mind. Having an OE hitch installed can be useful, weighed against any info you have on how hard it worked towing with the previous owner.

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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