This is a Briley diffusion choke designed to quickly disperse shot for a wider pattern at short ranges. It is for a 12 gauge Ruger Red Label and I'm selling it because I no longer own the gun. $30 TYD. Here is a review that gives a description of its use;
www.fieldandstream.com
Briley Diffusion Chokes
The Diffusion chokes are gently rifled, the idea being to spin the wad and disperse shot more quickly, giving you a quick-opening pattern for close range targets.
www.fieldandstream.com
