http://www.realoem.com/bmw/showparts...14&hg=64&fg=18

I bought #20 but didn't realize I don't have the right mounting posts. I think I need #17 in that picture but I cannot find the part number for #17 - I suspect its a nut with a peg on the end. My sisters 530i has it but for some reason my car (9/91 525) doesn't.

Any help?