I used the Bravo barrel extension on my first AR-15 barrel build, a 6mm ARC 21 & 3/4" barrel. The Extension fit the receiver perfectly and the threads and shoulder were very square to the barrel that I single point threaded. Great product and I received it within a few days of ordering it which was a nice surprise.
Not yet installed. Should come with an index pin and it did not. Pin not offered on the site?