5/16"-18 x 1-1/2" ASTM F879 Hex Drive 18-8 Stainless Steel Button Socket Cap Screw / THREAD CLASS: 3A THREAD DIRECTION: RIGHT-HAND THREAD LENGTH: 1.46 INCHES MINIMUM AND 1.50 INCHES MAXIMUM FASTENER LENGTH: 1.46 INCHES MINIMUM AND 1.50 INCHES MAXIMUM HEAD STYLE: C30 BUTTON HEAD DIAMETER: 0.527 INCHES MINIMUM AND 0.547 INCHES MAXIMUM HEAD HEIGHT: 0.152 INCHES MINIMUM AND 0.166 INCHES MAXIMUM INTERNAL DRIVE STYLE: D5 HEXAGON END ITEM IDENTIFICATION: 2355-01-539-3639 NOMINAL THREAD DIAMETER: 0.3125 INCHES WIDTH ACROSS FLATS: 0.1875 INCHES MINIMUM AND 0.1900 INCHES MAXIMUM THREAD QUANTITY PER INCH: 18 MATERIAL: STEEL OVERALL MATERIAL DOCUMENT AND CLASSIFICATION: ALLOY GROUP 1,ALLOYCONDITION CW PER ASTM F879 INTERNATIONAL STD/SPEC SINGLE MATERIAL RESPONSE OVERALL THREAD SERIES DESIGNATOR: UNRC