New idea, great result - Aero Precision M4E1 Enhanced 7in 5.56 Pistol Length Complete Upper Receiver with Flash Hider

I have built 2 rifles now with the this enhanced upper and hand guard setup. All I can say is that it looks and feels fantastic. Downside is that you are extremely limited to hand guard options. The Aero unit is a larger diameter so not everyones cup of tea. For me, it's a perfect fit but I have large hands. Lightweight, strong, and looks good.