SURFACE MAY BE WHOLLY OR PARTLY UNMACHINED;CORNERS MUST NOT BE SHARP;SURFACES MUST BE CLEAN AND DRY;GOETZE MATERIAL MED-131C SINTERED POWDER METAL PMF-10;APPARENT HARDNESS 70-100 HRB AT 0.25 INCHES EITHER END (CENTER APPARENT HARDNESS TO BE 60 HRB MIN)