Medium carbonAlloy steel, quenched and tempered in accordance with SAE J1199 material requirements and ANSI/ASME B18.2.3.1m dimensional tolerances. Compatible with class 10 hex nuts, all metal lock nuts or nylon insert locknuts. Metric mild or 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.