Carlsons has collected nearly 30 years of data about shotgun patterns and shotgun shell load data, since no two shotguns, choke and ammo combinations shoot alike. Carlson's proprietary computer software has compiled and collected all their information to provide the best possible choke tubes for your shooting needs. CNC machined from 17-4 heat treated stainless steel, the Carlsons choke tubes are made in the USA and will provide a lifetime of service and are backed by a lifetime warranty. The Carlson's Beretta Mobil/Benelli 20g Sporting clays extended choke tube is sold in a variety of constrictions like this Full and easily identified by the laser etching on the knurled end which makes changing the choke on the range or in the field a breeze. The Carlson's Beretta Mobil/Benelli 20g Sporting clays extended choke is blued for added durability in poor weather conditions.