Ring magnets are similar to disc magnets, but with a hole in the middle. They are often used in engines, speakers or as closures. If the ring magnets will be used in jewelry you should consider to choose a magnet with a coating of zinc or gold to avoid nickel allergy.
The magnetic poles are always located on the two flat sides of the magnets.
If you consider to mount the ring magnet with screw there are many other alternatives. You can see those below.