This barrel is perfect for a CQBR Block 2, Mk18 Mod 3 or FBI HRT build, or any other general purpose short barreled firearm. Colt makes superior grade chrome lined barrels, and the 11-1/2 models are very tolerant of different ammo, running suppressed or unsuppressed. 11.5" barrels are standard carbine gas system. No gas block or delta ring included. The SP401065 comes packaged lightly oiled in a milspec blue VCI bag and is ready to be used with your choice of rail for free floating installation.