Call Chico. They will tell you if the anchors can be used that way. I called about out GMC envoy and they couldn't be used with a seat in the middle I have looked in the manual of the X5 and it doesn't specify which I was surprised by because I was wondering if I could just put a car seat in the middle.

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2004 M3, Silver Grey, Blk, 6MT
2011 X5, 35d Sport Activity, Deep Sea Blue / Cinn Brown
2013 X5, 35i Sport Activity, Platinum Gray / Blk, AD