Carlson's 20 Gauge Sporting Clays Choke Tubes are molded from 17-4 stainless and machined to give you a Shotgun Choke tube that throws more effective patterns than standard choke tubes. These Choke Tubes manufactured by Carlsons Choke Tubes have a 25% longer parallel section, to throw some of the most consistent patterns you can achieve. For best results, pattern your Carlsons 20 Gauge Shotgun Choke for Sporting Clay with the specific shotshell load you will be using in the field. Lead, Copperplated, Nickel, Hevi-shot, Bismuth and Tungsten