The SG 556 Classic is the US civilian market import of the SG 550 system, with a thumbhole stock and 16-inch barrel to comply with importation requirements. Type: Rifle Action: Semi-Automatic Caliber: 5.56x45mm NATO Capacity: 30 Year introduced: 2006, Switzerland Weight: 118 oz Overall length: 38.9" Status: Active Intended use: Sport, Collecting