I found this older thread and thought I might get some insight on my questions. Keep in mind a few things while reading this. I'm only talking about the SIDE MARKERS. In front those have a yellow (amber lens). In the back they are red lenses. I have a Bentley Service manual and I also have the link mentioned above that list all bulb numbers and an alternative more common number. The list above gives a bulb number 1156 for the front side markers. I don't think so. My side markers use very small push in bulbs that look just like the little bulbs used in the old Brownie Cameras for the flash. If I need to post a pic I will. The 1156 bulbs are a round base and a regular shape bulb, much like the bulbs you would use in a lamp in your house. (of course much smaller than the ones in your house). The 1156 bulbs are used in my rear parking lights but not the side markers. Now my only question is this. Are the two red lens side markers on the rear SIDE of my Z3 supposed to have bulbs and light up? Because they do not and the Bentley manual only addresses the front (yellow lens) markers. The Bentley manual does not even mention the rear side markers. Any help here? Appreciate it.