I've had a set of Briley Companion tubes for about 10 years that I've never used. I have an older English sxs I'd like to try them in, its a 12 and the tubes are 20. I know about the balance etc. but I'm curious as to whether they may only be used with a gun they are fitted to or not. They fit in the gun I have very snugly and the extractors work. Anyone have any problems with them?

https://www.briley.com/c-416-companion-drop-in-tube-sets.aspx
"The advantage of the Companion series is that they are ready-made tubes that are shipped direct to you and do not require you to send in your barrel or gun."

The tubes I had were equipped with a small plastic not quite flush rod at the muzzle end to keep the tube tight.
There will be a significant build-up of powder residue and debris in the bore just past the end of the tube, and the bore will need to cleaned regularly.

Companion are made to fit a wide number of guns, but not all. Too small a bore, too large an overbore or short chambers might not work well. If your gun has 2 1/2” chamber you might have a fitting issue. You could measure your tube external chamber area at 2 1/2” and compare it with your chamber diameter of your gun. Or just gentle put them into your gun and see if they seat fully without any issues. I’d measure if you have the tools.

The .410 companion tubes tend to be easier to get into short chambers in my experience. I bought a set of old Briley skeet tubes, 20, 28 & .410 for $200.00 and cut them down to 20”. It reduced the weight and eliminated issues with chokes of the gun interference with seating. They were made for a very tight bore gun so they fit just about anything. If too loose I just add a bit of liquid nylon nail polish to the tubes. Fairly strong temporary thing to help fit. They are a lot like the old Browning Super tubes from the 60’s but with built in extractors. Weight is nicely between the hands.

Thanks for the comments. I think the chambers are longer than I would have expect as the tubes fit snugly but do not need to be "jammed" in. Likewise the front seem fully supported. I"ll give them a try over the weekend weather permitting. My 20ga loads are milder than factory so I shall see. Thanks again.