I bought mine from Amazon. Can't remember how much it cost me, but somewhere between $300-$400. Just go to Amazon and search for "SmartTop E89". Make sure it is the new plug-n-play style.

I originally was going to go to one of the authorized installers that is on the mods4car's website: http://www.mods4cars.com/sms/shop/. But I realized that I would be able to install it myself, and save a few bucks by buying it from Amazon. I think I paid $350 or so rather than the full price of $379.

BTW, the unit you want is the STLFBW3: http://www.mods4cars.com/sms/shop/in...de=view&id=112

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2011 Black Sapphire 30i Z4, Black Kansas Leather, Cold Weather Package, Premium Package, Sport Package, Comfort Access, Dark wood trim