This specification covers an aircraft-quality, low-alloy steel in the form of sheet, strip, and plate. These products have been used typically for heat treated parts, 0.875 inch (22.22 mm) and under in section thickness at time of heat treatment, requiring through-hardening to a minimum tensile strength of 180 ksi (1241 MPa) and proportionately lower strength in heavier thicknesses, but usage is not limited to such applications.