I think my Crossroad 450 bars are the 58". I have a shorter set from a previous vehicle, might be 50" or something similar, and they are slightly too short. They work, but the end caps fall off.

I would get the 58", and cut them to length with a hacksaw. The end caps pop on and off, and you can cut them exactly right. I left mine at full length because I want to be able to mount 3 bike racks, and 2 wheel holders.

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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