5/16"-18 Plain Finish Grade A Finished Hex Nut / THREAD CLASS: 2B THREAD DIRECTION: RIGHT-HAND NUT STYLE: A12 HEXAGON NUT HEIGHT: 0.258 INCHES MINIMUM AND 0.273 INCHES MAXIMUM END ITEM IDENTIFICATION: MRAP BUFFALO MK2A2 WIDTH ACROSS FLATS: 0.489 INCHES MINIMUM AND 0.500 INCHES MAXIMUM THREAD SERIES: UNC THREAD QUANTITY PER INCH: 18 HARDNESS RATING: 121.0 BRINELL STANDARD MINIMUM NOMINAL THREAD SIZE: 0.312 INCHES BEARING SURFACE TYPE: CHAMFERED OR WASHER FACED MATERIAL: STEEL OVERALL SURFACE TREATMENT: ZINC OVERALL SURFACE TREATMENT DOCUMENT AND CLASSIFICATION: SAE/AMS OR ASTM B633 ASSN STD SINGLE TREATMENT RESPONSE OVERALL