The SG 550 is an assault rifle manufacture by Swiss Arms AG (formerly Schweizerische Industrie Gesellschaft) of Neuhausen, Switzerland. The rifle is based on the earlier 5.56 mm SG 540 and is also known as the Fass 90 (Fusil d'assault 90 / Fucile d'assalto 90) in French / Italian or Stgw 90 in German (Sturmgewehr 90).