This is an incredible innovation bravo Aero for the easiest build I have ever done. I have used the shim type barrel nut hand guards and I thought there's got to be a better way and here it is. While the others aren't impossible, nothing is easier than putting the barrel in the upper receiver and torqueing. 5 stars for ease of use, 5 stars for quality and finish, 5 stars Toms Tactical for price and fast service. Perfect for the first time builder a little intimidated by the thought of building your own rifle don't hesitate to try with this combo