This specification covers a premium aircraft-quality, low-alloy steel in the form of bars, forgings, mechanical tubing, and forging stock. These products have been used typically for parts requiring a through-hardening steel capable of developing a minimum hardness of 53 HRC in nominal cross-sectional thickness 3.5 inches (89 mm) and under, and being capable of producing finished parts that may be required to pass stringent inspection standards, but usage is not limited to such applications. Certain design, processing procedures, or environmental conditions may cause these products to become susceptible to stress-corrosion cracking; ARP1110 recommends practices to minimize such conditions.