Poor mount design
The 1/4" mounting studs on these mirrors are not threaded into the base of the mirrors; they are simply stuck into a 1/4" round hole and secured with a small set screw. This design is very poor and totally inadaquate for proper mounting - the stud just pulls out of the mirror when tightening the nut. To make these mirrors work for me I had to thread the mirror holes to accept a 5/16" studs and used lock nuts to hold the studs in place. I bought these mirrors because they have 1/4" studs, which, it turned out I could not use. Had I known I would have to thread them for 5/16" studs I would have purchased different mirrors.