This is a very desirable original SIG model 556 "short-barreled" semi-automatic rifle. The original SIG 550 was developed for the Swiss Army by the SIG factory in 2006. This is the same basic rifle except it's semi-automatic and is a rare SBR. The left side of the receiver has the standard factory legend of "SIG 556 5.56 NATO SIG SAUER INC. EXETER. NH. USA". These desirable rifles use the ultra-reliable piston driven gas system instead of the gas impingement system of the AR15/M4 platform. This system keeps the inside of the receiver free from carbon build up that occurs during firing. It is fitted with a short "SIG/SAUER" marked perforated aluminum handguard with the Picatinny rail on all four sides as well as on top of the upper receiver for mounting various types of flashlights, laser and optical sights. Currently, it is fitted with a permanently attached front sight post and a detachable SIG adjustable rear sight. It has the short 10 inch barrel that has a standard M16A2 style bird-cage flash hider, and a two-position gas system. It has the original "Sig-Sauer" marked plastic pistol grip with a storage compartment inside and a folding 2 position telescoping buttstock. It include one "SIG/SAUER" marked polymer magazine, an instruction manual and SIG/SAUER blue plastic storage case.