Anyone know where these washers go?
 

I took off my door panel and mirrors last night and found some small, thin, nickle sized washers on the garage floor the next morning. Looks like neoprene washers and these things are very very thin. Didn't notice them falling out last night in the dark. Anyone know where these go? Looks like it might go on the mirror studs but I'd be guessing and don't know. Did a search and found nothing. Any help would be appreciated.

yes they do infact go on the studs....before the mirror is reinstalled.

Thanks!! OK so now I only have 3 of those things with the rest lost forever. So... before I go to Home Depot for more, what do those things do? I have already reinstalled so are they that important 'cause it doesn't seem that critical.