This Aero Precision M4E1 Threaded AR-15 upper receiver group comes completely assembled with 16” 5.56 barrel and the ATLAS R-ONE M-LOK handguard. This barreled upper receiver group does not include BCG or charging handle allowing you to choose your favorites for your build. The upper receiver is, however, fully assembled with forward assist and dust cover. The M4E1 threaded upper is made from forged 7075-T6 aluminum with a billet machined look that matches the lower and handguard. The ATLAS R-ONE free float handguard is 15” and features a 1.3” inner diameter that surrounds the low profile gas block and mid-length gas tube.