This ring is an outer ring that goes with same size inner ring :
Comfortable men's ring.
Insert the outer ring perpendiculary to the inner ring. Most rings are a little oval so that you may find a good angle. You need to force a bit but don't hit it with a hammer ! If it is too hard to insert you can use a thin sandpaper on the inside of the outer ring. For a finalised assembly it is recommanded to put tiny drops of metal glue on the inside of the outer ring. The whoole process should take around 5 minutes.
I will provide more ring sizes over the time. Feel free to request your's first !