A washer, round in shape, having a centrally located hole. one bearing surface is flat, the other surface is in the form of a raised shoulder (boss) having a flat bearing surface. either or both of the bearing surfaces must be broken by a counterbore, countersink, or similar shaped recess. the thickness of the shoulder (boss) must not exceed 25 percent of the shoulder (boss) diameter. for items having a shoulder (boss) of greater thickness, use bearing, sleeve; bushing, sleeve; or spacer, sleeve. excludes insulator, washer and thrust type washers.