The Maxim Defense PDX upper receiver is built to handle the fierce demands of the Tier 1 community and designed to install on any Mil-Spec lower receiver. With the PDX U.R.G, you dominate close-quarter encounters and achieve maximum energy on target without sacrificing accuracy at distance. At just 14" in overall length and a 5.5" barrel, the PDX U.R.G. is the ultimate choice for when concealment and personal defense is non-negotiable. The included HATEBRAKE increases reliability and is tucked under the M-Lok handguard. These upper receiver groups ship complete, including a Maxim Defense Mil-Spec or SCW bolt carrier group, Radian Raptor charging handle, and Maxim Defense hand stop, ready to shoot right out of the box. FeaturesIncreased reliability due to included HATEBRAKEM-slot compatible handguardMilitary-grade materials [17-4 Stainless Steel, 7075 and 6061 Aluminum]HK height rail for a more rigid upper receiverInstalls on any Mil-Spec lower receiver