This American Tactical: OMNI HYBRID model features a fully-patented metal reinforced polymer upper and lower receiver group. The Omni Hybrid lower features a patented hammer and trigger pin retainment system, preventing movement from the hammer and trigger pin during firing. It also features ATIs patented over-molded metal insert, which reinforces the buffer tube housing and rear takedown pin. This allows for metal-on-metal contact with both the buffer tube as well as the rear takedown pin, thus increasing strength and durability from recoil and consistent firing. This model also features a 16\" black nitride barrel and a 15\" M-Lok rail so you can attach all the accessories you need. This model ships complete with a 60 Rounds Quad Stacked Schmeisser Magazine and a Red/Green Multi Setting, Multi Reticle Reflex Sight. Lightweight, Versatile, and Accurate the Omni Hybrid will provide years of worry-free service at a price tag that won\'t break the bank. Click the \"show more\" tab for more info on the mag and optic. Mfg# - ATIGOMX556BFG60D