They must work Cookieman, they have been around forever!!! I can remember when only the rich guys had them. It would really make a single barreled H&R shotgun be capeable of doing everything, and easy to change the choke in the field also. I would think it might even help to tighten up slug groups, set your choke to whatever setting the slugs shot best at. I guess the final cost would be about $120 with shipping both ways....<><.... :grin: