5/16" UNC Hex Nut - Galvanised Mild Steel - BS 1768 - Tapped Oversize Since hot-dip galvanizing typically adds 2.2 to 5 mils of thickness to the threaded portion of a fastener, galvanized heavy hex nuts are tapped oversize to compensate for the corrosion resistant coating on the thread of the bolt Dimensions: 5 /16" x 18 TPI 14 mm Across the flats 12 mm Point to Point 6 mm thickness