$88.64
I.O. Inc. AR15 Barrel, M4 Profile, 223 Rem/556NATO, 16", Black Finish 13010125
$708.49
Colt's Manufacturing Complete Upper Receiver, 223 Rem/556NATO, 16.1" M4 Barrel, Black Finish, A2 Fixed Front Sight, Magpul BUIS Rear Sight LE6920CK