I went with the Tekonsha wireless brake controller and it was easier to deal with. But you do have to mount the wireless receiver on the tongue of your trailer so you have a big box there. It works great tho!

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2007 328i Sport, Monaco Blue
2011 X35D - sold -Space Grey
2004 X5 4.4i - sold - Kalahari Beige
2001 X5 3.0i - sold - Pearl Beige
2006 325i Sport, Sonora Beige
2000 323i - sold - Sienna Red