Driver's mirror was a little wobbley on door, bouncing around on rough pavement made it hard to see backward.... It was not apparent how to get it tighter, and no nuts were inside the door when I felt around in the back while replacing the speakers. Turns out that you just have to give the mirror unit a firm twist, which exposes the two mounting bolts. I removed, cut an additional sticky-backed foam gasket, and it tightened back up.... fixed!