SIG-SAUER SIG-556 ER Carbine. Features a 16” military grade cold hammer forged bbl, chambered in 5.56mm NATO, with a twist rate of 1 in 7”. The flash suppressor uses a standard .5 x 28 TPI thread pattern, ensuring compatibility with after-market accessories. The forearm housing the gas operating system is a vented non-slip polymer featuring the SIG TriRail design with three integrated Picatinny rails for mounting accessories. Flat top receiver. The flip up front combat site is adjustable for windage and elevation. The Picatinny rail equipped receiver is made of high strength steel with a durable wear-resistant Nitron X rifle finish. The Picatinny rail features a flip up rear sight that works in concert with the front combat sight, providing iron sight performance and a back up sight option for optics. The trigger housing is machined from an aircraft grade aluminum alloy forging with a hard-coat anodized finish designed to survive extreme conditions. The rifle comes equipped with a smooth two-stage trigger, ambi safety and is designed to accept standard AR magazines. One 30-round mag is supplied. Folding stock with the ability to collapse, providing he best of both worlds. It has a rubber butt pad & multiple sling attachment points. OA Length 37". Length w/ Stock Collapsed 33.5". Sight Radius 21". Forearm Polymer SIG TriRail. Weight w/o Mag 7.8 lbs. Operating System Gas Operated, Rotating Bolt