Carlson's Choke Tubes Retay Cremator Ported Waterfowl 20 Gauge Choke Tube .592 Stainless Steel. TST is a series of three graduated rings in the taper section of the choke tube that allows a more gradual transition from the shotgun bore to the final constriction. This design offers reduced pellet deformation less flyers and more dense patterns. These benefits make the Cremator Series extremely effective on all types of waterfowl throughout the entire season. The Cremator series has no size or speed restrictions with steel shot in any of the three constrictions. You also get all the benefits of an extended choke tube including a 25percent longer parallel section for tighter and more dense patterns wrench-less installation quick removal and helps with muzzle protection. Specifications for Carlson's Choke Tubes Retay Cremator Ported Waterfowl 20 Gauge Choke Tube: Manufacturer: Carlson's Choke Tubes Color: Stainless Steel Fabric/Material: Stainless Steel Gauge: 20 Choke Tube System: Retay Choke Package Contents: Carlson's Choke Tubes Retay Cremator Ported Waterfowl 20 Gauge Choke Tube Carlson's Choke Tubes 11479: Retay Cremator Ported Waterfowl 20 Gauge Choke Tube .592 Stainless Steel