Hi Steve,
You will be confused with all these tips! The round mirrors that came with my Roadster were impossible to adjust, and were replaced with other round mirrors that are great - until a lense dropped out, never to be seen again.
When I got the replacements, they slipped out of lower stem complete with light grey plastic band with a cut-out which I guess is where the clamping screw bites? The black collar fits over the top of the lower stem to keep water out? The new tops arrived assembled with these plastic/rubber bits
Don't understand why yours do not separate, unless - WD40 overnight might free it?
Good Luck.
