This one got me beat , I have non power mirrors with the three metal fingers on the inside of the glass , it looks like it will only slide towards the truck as the circular base has a half round stopper on one side , I tried just sliding it over but it won't go and I cant see any release tab for a screwdriver , how do you get this glass off ???????????????????

 

Plastic housing or metal?

Mine were attached to the backing with clear silicone globs. I used a sharp, thin putty knife and slowly sliced the glass off....

 

They are plastic tow mirrors the back side looks like this, I can't figure out how to release them for removal,