Good afternoon! I'm listing my aero precision m4e1 complete upper receiver, it is chambered in 5.56 and the barrel length is 10.5. It came from one of Aero Precision limited builder sets. It works perfect has about 300 rounds through it and functions just as it should it has an aero precision non-adjustable gas block and carbine gas tube. For the muzzle device it has a strike industries sail compensator. Will through in lantec EBCG or sig msr for additional cash will however include the radian charge handle.