Sample is dedicated to electric kettle (electric tea kettle) pump above the ring magnet, the material is ferrite, with the ordinary ring is different from the distribution of its surface 4 poles, and there is a small pit to distinguish between the strong magnetic surface, the specific dimensions of the outer diameter of 20.5mm, hole diameter of 7.5mm, the thickness of 4.5mm (there are some customers using 3mm thickness, we also have), the surface magnetic strength of 1200 gauss! If you want to get the price, samples, please inquire.
Sample image of axial 4-pole ferrite magnet ring 20.5x7.5x4.5mm;
It may be better suited to your specifications;