Carlson's Choke Tubes Cremator 12 Gauge Retay Ported Waterfowl Choke Tube Mid Range/Long Range .697 .707 Black. 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. They are offered in your choice of ported or non-ported configurations. Specifications for Carlson's Choke Tubes Cremator 12 Gauge Retay Ported Waterfowl Choke Tube: Manufacturer: Carlson's Choke Tubes Color: Black Fabric/Material: 17-4 Stainless Steel Gauge: 12 Choke Tube System: Retay Choke Choke Type: Mid-Range/Long-Range Diameter: 0.697 in 0.707 in Gun Make: Retay USA Shotguns Quantity: 2 Length: 3.75 in Package Contents: Carlson's Choke Tubes Cremator 12 Gauge Retay Ported Waterfowl Choke Tube Carlson's Choke Tubes 11582: Cremator 12 Gauge RETAY Ported Waterfowl Choke Tube Mid Range/Long Range .697 .707 Black