The Geissele Super Duty MOD1 14.5" Heavy Barrel Complete Upper Receiver in Black is a high-quality upper assembly built around a robust cold hammer forged barrel with a heavy profile and a .750″ gas journal for enhanced rigidity and heat capacity. With a 1:7 twist and chrome-lined rifling, the barrel is optimized for a wide range of 5.56 NATO ammunition. The MOD1 upper features a mid-length gas system with a Super Compact gas block, an MK16 M-LOK free-float handguard, and is optics-ready with a full Picatinny rail. Sold as a complete upper, the 08-626B provides the core components needed to build a durable, precision-oriented AR-15 platform when paired with a compatible lower receiver and lower-end parts.