External Hex, Internal Hex, Internal Torx, TX, Hex
Imperial, AF, Metric, Torx, SAE
4 mm, 5/16 ", 5/8 ", 5.5 mm, 7/16 "
1/2, 1-1/2, 3/4, 3/8, 2-1/2
25.4, 6.35, 9.53, 38.1, 19.05
Special Steel, Molybdenum Steel, Alloy Steel, Steel, Chrome Molybdenum Alloy Steel
Gun-metal, Phosphatized, Oxidised, Black Phosphate, Black Oxide