5/16"-18 x 1-1/2" ASTM F879 Hex Drive 316 Stainless Steel Button Socket Cap Screw / THREAD CLASS: 3A THREAD DIRECTION: RIGHT-HAND THREAD LENGTH: 1.500 INCHES NOMINAL FASTENER LENGTH: 1.500 INCHES NOMINAL 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: 016217138 NOMINAL THREAD DIAMETER: 0.3125 INCHES WIDTH ACROSS FLATS: 0.1875 INCHES MINIMUM AND 0.1900 INCHES MAXIMUM THREAD QUANTITY PER INCH: 18 SPECIAL FEATURES: MULTIPLE DISTRIBUTORS MAKE ITEM MATERIAL: STEEL COMP 316 OVERALL THREAD SERIES DESIGNATOR: UNC