In 1958, as part of a rank restructuring, two pay grades and four ranks were added: sergeant (E-5) returned to its traditional three chevron insignia, E-6 became staff sergeant, which had been eliminated in 1948 (with its previous three chevron and one arc insignia), sergeant first class became E-7, master sergeant became E-8, which included first sergeant and specialist 8; and E-9, which included sergeant major and specialist 9.