These discs are "diametrically magnetized," which means that the poles are located on opposite sides of the circular shape, not in the center of the circular flat surfaces like most disc magnets. The magnets will tend to want to line up side-to-side rather than stack on their flat surfaces. The unusual magnetization makes them an interesting disc to experiment with.
These discs are often used with Hall Effect switches and sensors.
This size is also available axially magnetized
in grade N52 with silver nickel plating as part number D42-N52
, in grade N42 with silver nickel plating as part number D42
, in grade N42 with black epoxy coating as part number D42E
, and in grade N52 with black nickel plating as part number D42B-N52