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 typically used for parts requiring through-hardening capability up to 3.5 inches (89 mm) in nominal thickness and subject to rigid magnetic particle inspection standards, but usage is not limited to such applications.Certain design and processing procedures may cause these products to become susceptible to stress-corrosion cracking after heat treatment; SAE ARP 1110 recommends practices to minimize such conditions.