This specification covers a premium aircraft-quality alloy steel in the form of bars, forgings, and forging stock.

These products have been used typically for parts requiring a combination of high strength, high toughness, and weldability, but usage is not limited to such applications. Product after proper heat treatment should attain a minimum tensile strength of 290 ksi (1999 MPa) and yield strength of 245 ksi (1689 MPa).