1/4" by 20 TPI nylon screws secured by nylon lock nuts. These take the place of (and are an improvement over, I think) the brass rivets used by BMW.
IMG_2914_Clearview.JPG 2010:08:21 16:08:11 Focal length: 49.0 mm Lens: 17.0 to 55.0 mm 1/160 sec, f/5 Mode: Program ISO: 200 AF mode: AI Focus AF White balance: Auto Flash: Off File size: 5,313KB Image size: 3504 x 2336