the rear air suspension is just self-leveling, that's the only reason it has it, I believe you get an extra 1000lbs towing capacity with it

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2006 BMW X5 4.8is Lemans Blue/Beige/Dark Maple
-Nav, Comfort Seats, Heated Steering Wheel,
Rear Airbags, AUX Input
2009 BMW M3 Space Grey/Black/Carbon
-all options