The MK12 AR15 style Upper Receiver Group is constructed around an 18-inch Stainless Steel barrel with a chamber created during the Cold Hammer Forging process, which ensures the most precise alignment of the chamber to the bore possible. This, along with being DLC finished, equates to unprecedented accuracy and durability. The MK12 barrel is engineered with a rifle-length direct impingement gas system and utilizes the MK12 gas block, which is built to Crane (Naval Surface Warfare Division) Specifications for USSOCOM. The upper receiver is equipped with a 12 inch free floating picatinny quad rail for your choice of optics and accessories, independently ambi GRIP-N-RIP Charging Handle that accommodates left- and right-handed shooters, and is finished off with a Daniel Defense Improved Flash Suppressor. All Daniel Defense complete upper receiver groups come standard with an M16 profile bolt carrier group.