There are two types of rings that you can make: rings where you use inlay materials, like crushed opal or abalone, for example, and rings where you turn ring blanks of wood, acrylic or other materials.
Inlay ring cores don't require blanks, but use a different technique where the groove in the ring is filled with inlay materials.
There are two styles of ring cores that require blanks:
Lifestyle one-piece rings can be made on a 7 mm pen mandrel using bushings small, medium or large according to the size of the ring you are making. These ring cores are made in USA. You can learn more about how to make Lifestyle rings here.
JDG two-piece rings require a special ring mandrel, which you select according to the size of the ring that you are making. This is a higher end product and ring cores are made in Ontario. You can learn more about how to make JDG rings here.