If you do some searching you will find that there are quit a few of them out there. You can find them listed by a few different names such as shotgun adapters, chamber mates, barrel reducers, and so on. You can find them in many different calibers. They range from about 4" long to full barrel length. Some places will custom make them to order. I own a few of the 4" converters in 12ga/20ga, 20ga/.410, and .410/.22. They all work really well in my opinion. I get point of aim from the .410/.22 adapter out to around 25yrds easy. I have aslo found that they all fit together nicely to allow me to use any combination of the bunch. Very convenient to have on hand in a survival situation.