This specification covers an aircraft-quality, low-alloy steel in the form of heat-treated bars 1.50 inches (38.1 mm) and less in diameter or least distance between parallel sides.
This specification covers a premium aircraft-quality steel in the form of bars, forgings, mechanical tubing, and flash-welded rings up to 5.000 inches (127.00 mm), inclusive, in diameter or least distance between parallel sides, and stock of any size for forging or flash-welded rings.