Self-aligning ball bearings have two rows of balls and a common sphered raceway in the outer ring. The bearings are insensitive to angular misalignment of the shaft relative to the housing. Self-aligning ball bearings generate less friction than any other type of rolling bearing, which enables them to run cooler even at high speeds. Self-aligning ball bearings are double row, self-retaining units comprising solid outer rings with a concave raceway, inner rings with a cylindrical or tapered bore and ball and cage assemblies. The bearings are available in open and sealed versions.