5/16" Shoulder x 3/8" Shoulder Length x 1/4"-20 18-8 Stainless Steel Socket Shoulder Bolt / THREAD CLASS: 3A THREAD DIRECTION: RIGHT-HAND THREAD LENGTH: 0.440 INCHES NOMINAL FASTENER LENGTH: 0.810 INCHES NOMINAL HEAD STYLE: C66 KNURLED NO. 1 HEAD DIAMETER: 0.438 INCHES NOMINAL HEAD HEIGHT: 0.220 INCHES NOMINAL SHOULDER DIAMETER: 0.313 INCHES NOMINAL SHOULDER LENGTH: 0.380 INCHES NOMINAL INTERNAL DRIVE STYLE: D5 HEXAGON END ITEM IDENTIFICATION: INTERCONNECT NOMINAL THREAD DIAMETER: 0.250 INCHES WIDTH ACROSS FLATS: 0.156 INCHES NOMINAL THREAD QUANTITY PER INCH: 20 SHOULDER SHAPE: ROUND FIRST SHOULDER MATERIAL: STEEL COMP 302 OVERALL THREAD SERIES DESIGNATOR: UNC