Here are two rings I made and since the ring shank I used was really narrow (14 gauge wire), I want to show you the set up I used for soldering.
Normally I solder with a third-arm holding the ring shank and then I just put the bezel on top and sweat solder. (Like for these rings)
That wouldn't work with the tube bezels. The bezels are too heavy and awkward to sit atop a thin piece of wire without falling.
So I got some greening pins (100% steel pins used in floral arrangements... easy to find on Amazon or at local craft supply stores).
I then placed the tube upside-down on the soldering pad and it was super easy to align the filed divots of my ring shank with the tube walls.
As I said, the pins are steel, so it's the same as when you use binding wire to hold things.