Carlsons Remington Flush Choke Tube 20 Gauge, Improved Cylinder Md: 51202 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).