This is a samarium cobalt permanent magnet ring with a diameter of 12mm and a thickness of 3.8mm. A sinker is a deep hole or sinker in the central part of the magnet. This design allows the magnet to provide greater magnetic field strength and more uniform magnetic field distribution, especially at the bottom of the sink hole, can maintain good magnetic properties in high temperature, wet or corrosive environments, can increase the plating.
Measuring the thickness of the flat sinking magnet ring 3.8mm thickness;
Samarium cobalt permanent magnet knowledge post;