The current U.S. Air Force Service Dress Uniform, which was initially adopted in 1994 and made mandatory on 1 October 1999, consists of a three-button coat with silver-colored buttons featuring a design known as "Hap Arnold wings", matching trousers, and either a service cap or flight cap, all in Shade 1620, also known as "Air Force Blue". This is worn with a light blue shirt (Shade 1550) and a herringbone patterned necktie (Shade 1620). Silver mirror-finish "U.S." pins are worn on the lapels. Officers' coats feature epaulets on the shoulders, while enlisted airmen have plain shoulders.