5/16"-18 Grade A Zinc Finish Steel Jam Top Lock Nut / THREAD CLASS: 2B THREAD DIRECTION: RIGHT-HAND LOCKING FEATURE: PREVAILING TORQUE ALL METAL DESIGN LUBRICATION: WAX NUT STYLE: A12 HEXAGON NUT HEIGHT: 0.180 INCHES MINIMUM AND 0.195 INCHES MAXIMUM END ITEM IDENTIFICATION: MRAP-BUFFALO A1 WIDTH ACROSS FLATS: 0.489 INCHES MINIMUM AND 0.502 INCHES MAXIMUM THREAD SERIES: UNC THREAD QUANTITY PER INCH: 18 NOMINAL THREAD SIZE: 0.3125 INCHES BEARING SURFACE TYPE: CHAMFERED PART NAME ASSIGNED BY CONTROLLING AGENCY: 5/16-18 ZINC FINISH GRADE A JAM TOP LOCK NUT MATERIAL: STEEL OVERALL MATERIAL DOCUMENT AND CLASSIFICATION: GRADE A STEEL IAW IFI-100/107 ASSN STD SINGLE MATERIAL RESPONSE OVERALL SURFACE TREATMENT: ZINC OVERALL SURFACE TREATMENT DOCUMENT AND CLASSIFICATION: FE/ZN 3AT IAW ASTM F1941 ASSN STD SINGLE TREATMENT RESPONSE OVERALL