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

These products have been used typically for parts requiring through-hardening to a minimum hardness of 50 HRC in section thicknesses up to 12 inches (305 mm) with a combination of high strength, fatigue resistance, ductility, and thermal stability for operation between -100 to +1000 \mDF (-73 to +538 \mDC), but usage is not limited to such applications.