Carlson's 12 Gauge Choke Tube. Replacement for Beretta Benelli Mobil Choke Tube System. Improved Cylinder.p Carlson's Flush Mounted Choke Tubes are available for most shotgun models and serve as a perfect replacement to damaged, worn out or misplaced factory flush mounted choke tubes. Carlson's Flush Mounted Choke Tubes are manufactured from corrosion resistant 17-4 PH Stainless Steel, they are compatible with steel or lead shot (Steel shot should not be used in any Turkey Choke Tube), and are backed with a lifetime warranty.