External Hex, Internal Hex, Internal Torx, TX, Hex
Imperial, AF, Torx, SAE, Metric
5/16 ", 5.5 mm, 18 mm, 1/4 ", 5/8 "
1, 2-1/2, 1-1/2, 1/2, 3/8
9.53, 38.1, 6.35, 25.4, 19.05
Special Steel, Molybdenum Steel, Alloy Steel, Steel, Chrome Molybdenum Alloy Steel
Phosphatized, Gun-metal, Oxidised, Black Oxide, Black Phosphate