This specification covers an aircraft-quality, low-alloy steel in the form of bars, forgings, mechanical tubing, and forging stock.

These products have been used typically for heat treated parts up to 4 inches (1102 mm) round or equivalent cross-section which require through hardening to tensile strength not lower than 180 ksi (1241 MPa) and which may require welding after heat treatment, but usage is not limited to such applications.