SBB have two rows of balls, the outer ring has a common concave spherical raceway, and the center of curvature is the same as the center of the bearing. Even if the inner ring, the steel ball and the cage are slightly inclined relative to the outer ring, they can rotate. Therefore, the bearing is self-aligning and will not be affected by the misalignment of the shaft relative to the bearing housing. It is mainly used to bear radial load, but can also bear a small amount of axial load, and generally cannot bear pure axial load. It is especially suitable for bearing applications where considerable shaft deflection or misalignment may occur.