Stag 15 Tactical Uppers are chambered in 5.56 NATO and built around a 16" barrel with a 1/7 twist rate. The free-floating Stag 13.5" M-LOK Handguard features a slim, lightweight profile that offers increased ergonomics, maximum airflow, and modularity while continuing to provide the utmost strength and durability. The handguard provides an uninterrupted picatinny rail along the top which allows room for sights, optics and accessories the shooter may require. These rifles have an A2 Flash Hider to reduce muzzle flash and a mid-length gas system, that is combined with a low-profile gas block, which provides reliability under any condition. Federal law requires this product to be transferred through a licensed FFL dealer. Stag Arms requires a copy of the dealer's FFL for verification. It's the customer's responsibility to notify the dealer of the order.