Neodymium ring magnets are disc magnets or cylinder magnets with a plain hole through the center of the magnet. It should be measured by outer diameter (O.D.), inner diameter (I.D.), and thickness (H). Likewise disc magnet, ring shaped magnet can be magnetized with its N pole and S pole opposite flat end surfaces or diametrically magnetized so as to the N pole is on one curved side and the S pole is on opposite curved side. Because of their magnetic strength, neodymium ring magnets are the preferred choice for many consumer, commercial and technical applications.