Yes, as the above poster' s said...Briley does make some great tubes but I think Dan might be talking about chamber inserts. Browning make some that the call " Little Skeeters" , they simply allow you do go down a gauge with an aluminum adapter.

Seminole Gunworks makes probably the best chamber inserts but they are quite expensive, you can buy a cheap gun like a M870 for the price of there inserts. But on a good note, these things are amazing, you have to actually see them perform to believe how they pattern.

try this link.....
http://www.chambermates.com/
AA