1/4"-20 Grade C Zinc Finish Steel Top Lock Nut / THREAD CLASS: 2B THREAD DIRECTION: RIGHT-HAND LOCKING FEATURE: TOP LOCK LUBRICATION: WAX NUT STYLE: A12 HEXAGON NUT HEIGHT: 0.212 INCHES MINIMUM AND 0.288 INCHES MAXIMUM END ITEM IDENTIFICATION: MRAP - COMMON NSN - USED ON 3 MRAP VARIANTS AND 19 OTHER WEAPON SYSTEMS WIDTH ACROSS FLATS: 0.428 INCHES MINIMUM AND 0.438 INCHES MAXIMUM THREAD SERIES: UNF THREAD QUANTITY PER INCH: 20 NOMINAL THREAD SIZE: 0.250 INCHES BEARING SURFACE TYPE: FLAT MATERIAL: STEEL OVERALL SURFACE TREATMENT: ZINC OVERALL SURFACE TREATMENT DOCUMENT AND CLASSIFICATION: ASTMF1941 ASSN STD ALL TREATMENT RESPONSES OVERALL