There are two types, one-way and two-way. In order to allow installation errors, either one-way or two-way, the spherical self-aligning spherical cushion type or seat ring type with spherical surface can be selected. 3. High quality steel - ultra clean steel which can prolong the bearing life by 80% at most 4. High grease technology - NSK lubricant technology can prolong the grease life and improve the bearing performance 5. High grade steel ball - quiet and smooth when rotating at high speed 6. Using the ferrule in the option, installation error can be allowed.