This is a relatively high height hollow cylindrical ferrite magnet, sintering process, radial 2 pole magnetization, also called ferrite rotor magnet, outer diameter 20mm, hole 6mm, height 45mm, mainly used for water pump motors, can be molded with other parts of the injection molded into one, need this size welcome to contact customer service quotes, there are other sizes, different materials.
Other popular sizes;
Water pump motor 4 pole permanent ferrite magnet hole 4.4mm
Water pump 4 pole radial ferrite magnet rotor 14mm x 5.2mm x 28mm