5/8"-18 ASTM A563 Grade A Zinc Finish Steel Jam Nut / THREAD DIRECTION: RIGHT-HAND NUT STYLE: A12 HEXAGON NUT HEIGHT: 0.387 INCHES NOMINAL WIDTH ACROSS FLATS: 0.937 INCHES NOMINAL THREAD SERIES: UNF THREAD QUANTITY PER INCH: 18 NOMINAL THREAD SIZE: 0.620 INCHES BEARING SURFACE TYPE: FLAT PART NAME ASSIGNED BY CONTROLLING AGENCY: NUT,HEX JAM MATERIAL: STEEL OVERALL SURFACE TREATMENT: CHROMATE ZINC OVERALL