This specification covers a premium aircraft-quality, low-alloy, heat-resistant steel in the form of bars, forgings, mechanical tubing, and forging stock. These products have been used typically for parts, such as compressor discs, turbine discs, shafts, and fasteners for use in service up to 1000 °F (538 °C) and subject to stringent magnetic particle inspection standards, but usage is not limited to such applications.