This specification covers an aircraft-quality, low-alloy steel in the form of sheet, strip, and plate. These products have been used typically for thick-section heat treated parts requiring good tensile and endurance strengths in combination with good ductility, but usage is not limited to such applications. The product may be through-hardened to tensile strength ranges of 260 to 280 ksi (1792 to 1931 MPa) in nominal section thickness of 1.5 inches (38 mm) and under and 180 to 220 ksi (1241 to 1517 MPa) in nominal section thicknesses 3 inches (76 mm) and under.