Part numbers for the A pillars vary depending on which side and color you need. If your interior is black, you'll want to order Anthrizit. If it's grey/tan, you'll want to order Sandgrau.
http://www.realoem.com/bmw/showparts...70&hg=51&fg=40 Black Left-51438189191 $31.76@ getbmwparts.com
Black Right-51438189192 $31.76@ getbmwparts.com
Grey/tan Left-51438189189 $35.72@ getbmwparts.com
Grey/tan Right-51438189190 $35.72@ getbmwparts.com