Thrust ball bearings with flat back face are separable and divided into single direction and double direction designs. The single direction thrust ball bearings with flat back face can only be used to carry axial load in one direction and limit the axial displacement in single direction. The double direction thrust ball bearings with flat back face can be used to carry axial loads in both directions and limit the axial displacements in both directions. Nether of them can carry radial loads.