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Oberstabsfeldwebel (OStFw or OSF, ) is the highest Non-commissioned officer (NCO) rank in German Army and German Air Force. It is grouped as OR9 in NATO, equivalent to a Sergeant Major in the United States Army and a Warrant Officer Class 1 in the British Army. Attainment of this rank requires at least sixteen years since promotion to feldwebel and at least six years since promotion to hauptfeldwebel