6. Size: 1/4 inch-20 X 1/2 inchFlat Head, Phillips DriveUse with nuts or pre-threaded holes of the same diameter & thread sizeOften used in machinery & appliancesNuts and washers not includedThread Type: Coarse, Thread Class: UNC-2A, Point Style: BluntSpecification(s) Met: ASME B18.Machine Screw, Flat Head, Phillip Drive 1/4in-20 X 1/2in Zinc Plated Steel 100PK They are frequently used in machinery and appliances.3 & SAE J82.