Carlson's Choke Tubes Rifled Chokes 20 Gauge Benelli Crio Choke Tube Rifled Choke Black. Each choke tube protrudes .625 to 1.3 inches from the end of the barrel depending upon which type of firearm the choke tube has been specifically designed for. Each choke tube has a right hand rifle twist which is 1 to 35. Each choke tube has a groove diameter of .730 of an inch in 12 ga. These choke tubes have a matte black finish and carry a lifetime warranty. If you're looking for improved accuracy from a smooth bore barrel these fine choke tubes will improve y Carlson's groups. Specifications for Carlson's Choke Tubes Rifled Chokes 20 Gauge Benelli Crio Choke Tube: Manufacturer: Carlson's Choke Tubes Color: Black Fabric/Material: Heat-Treated 17-4 Stainless Steel Gauge: 20 Choke Tube System: Benelli Crio Choke Type: Rifled Gun Make: Benelli Quantity: 1 Country of Origin: USA Features of Carlson's Choke Tubes Rifled Chokes 20 Gauge Benelli Crio Choke Tube Extended Rifled Choke 1-35 Rifle Twist For use with all slugs rifled slugs and sabots Package Contents: Carlson's Choke Tubes Rifled Chokes 20 Gauge Benelli Crio Choke Tube Carlson's Choke Tubes 40071: Rifled Chokes 20 Gauge Benelli Crio Choke Tube Rifled Choke Black