A washer, round in shape, and having a centrally located hole. one bearing surface is flat and unbroken, the other surface is in the form of a raised shoulder (boss) having a flat bearing surface. 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.