Self-aligning ball bearings are constructed with the inner ring, ball assembly, out ring with a spherical raceway and cage assemblies. The bearing has the self-aligning performance. Thus, to some extent, the axis of inner ring can deflect around the bearing center. Under normal load, the inclination of the outer ring and inner ring should not exceed 3 degrees. The material of the cages is steel, synthetic resin and so on. Open type and sealed type bearing is available in TBB.