Alloy steel, quenched and tempered in accordance with SAE J429 material requirements and ANSI/ANSI B18.2.1 dimensional tolerances. Compatible with UNC grade 8 hex nuts, all metal lock nuts or nylon insert locknuts. USS or SAE hardened flat washers as well as helical spring lock washers may also be used with these cap screws for a complete assembly. Cap screws are zinc yellow finish.