If you are installing the aero precision ar15 bar barrel nut you will need these - Aero Precision AR15 BAR Shim Pack

I have built numerous ARs and love Aero Precision for the most part. However, when attempting to install the Aero Precision AR15 BAR Barrel Nut and Shims I hit a wall. I encountered numerous issues trying to properly align the nut to accept the handguard on my Aero Precision M4E1 Threaded Assembled Upper Receiver. I was unable to adequately shim the nut for my application with the four shims that were included so I had to order the Shim pack. After some effort . . this solved the problem.

Dave H.