Internal Hex, External Hex, Internal Torx, Hex, TX
AF, Metric, Torx, Imperial, SAE
5/16 ", 9/16 ", 3/16 ", 19 mm, 1-1/2 "
6.35, 9.53, 19.05, 25.4, 38.1
Special Steel, Molybdenum Steel, Alloy Steel, Steel, Chrome Molybdenum Alloy Steel
Phosphated, Phosphatized, Oxidised, Black Phosphate, Black Oxide