Features The contact surface with the bottom of the container is small, so it is suitable for high rotation use. It contains expensive samarium cobalt (Smco) magnets and has an inert carbon mark (black) for easy identification. It can be used for quite a long time because it is not only strong magnetic force but also has little deterioration of magnetic force compared to conventional Alnico magnets. Spec Diameter x total length: 8 x 25mm