Carlson's Remington Pro Bore 12 Gauge Turkey Choke Tube. .665 Constriction Carlson's Remington Pro Bore Extended Turkey Choke Tube extends approximately 1" from the end of the barrel. They are manufactured from 17-4 heat treated stainless steel and have a matte blue finish. The Extended Turkey Choke Tubes feature a 1.050" parallel section to produce the optimum pattern with your shotgun. For lead or hevi-shot only.