Mazda B4000 (Ranger) outside mirrors question

I have a 1997 Mazda B4000, 4.0L V6, 4WD. The truck has two outside rearview
mirrors. One of them appears to be ever so slightly loose -- I adjust it
for a good view of the rear and after a few days of driving it has slipped
out of adjustment. Is there anyway to open these things and tighten the
mounts? These are the OEM mirrors -- the mirror is enclosed in a plastic
housing. They are manual adjust, not power.

Thanks.