I had to special order my +2 extension for my SN from Brownells, no problems as it came to just under $100 with shipping but it took 2 months to get it because it wasnt in stock. Well worth the wait, I thought they sent me an empty box until I realized how lightweight it is. Fits excellent and the removable endcap lets me reuse the spring retainer so it can be threaded on without fighting the spring pressure. Its too bad they didnt extend it flush with the barrel, it would have took 7 2 3/4" shells in the tube if they did.