This might be too late to help you out, but be very careful when you remove the grillls. Over time they get as brittle as a ricecake, and usually when you try to remove the fastener the post breaks off. The original BMW fastener is overkill. I suggest that you do what I did which is to use a piece of rubber tube with just a dab of model glue to attach to the post from inside the fender. Don't forget to blackout the area behind the grill for an OE appearance which disguises the fact that these vents are fake!.