These rings are diametrically magnetized, which means they are magnetized perpendicular to the axis of the hole. The poles are located on opposite sides of the circular faces. They can be placed on a shaft to work with sensors or to generate electricity. They can also be used to fish wires through a finished wall by pulling them with a larger magnet from the outside.
This size is also available axially magnetized
in grade N52 as part number RC4C-N52