"T/C 12ga Ext Turkey .660 Description Carlson's Extended Turkey Choke Tubes extend approximately 1"" from the end of the barrel. They are manufactured from 17-4 heat treated stainless steel and have a matte blue finish. Our Extended Turkey Choke Tubes feature a 1.050"" parallel section to produce the optimum pattern with your shotgun.? Note: Not for use with steel shot. - Caliber: Tru-Choke 12 Gauge - Constriction: Turkey - Diameter: .660"