Carlsons Tubes Flush Mount Cylinder Choke Tube Features The Carlsons Tubes Flush Mount Cylinder Choke Tube threads into the Invector pattern found on Winchester Mossberg 500 Browning Invector Weatherby and Savage 12 and 20 gauge shotguns giving owners of these platforms a factory-fit upgrade without sending the barrel out for threading. The .620 diameter bore is held to tight tolerances so patterns stay consistent shot after shot which matters most when a true cylinder choke is asked to spread shot evenly at close range. Because the tube sits flush with the muzzle there is no external choke extension to catch on brush a blind or a gun case during a day afield. This low profile design keeps the barrel s balance and handling unchanged from the factory configuration. Built from 17-4 heat treated stainless steel the tube resists the corrosion and wear that high volume shooting and outdoor exposure bring extending its service life well beyond softer alloys. It is rated safe for steel lead copper plated nickel Hevi-Shot and bismuth shot so a shooter rotating between dove loads steel waterfowl loads and dense tungsten style pellets never has to second guess compatibility. The Invector thread pattern also fits Mossberg Accu-Choke and Weatherby threaded barrels widening the pool of shotguns that can use this single tube. For a shooter who needs a reliable close range cylinder choke for upland birds dove fields or close presented clays this tube is a straightforward factory replacement available for sale at GrabAGun. Carlsons Tubes Flush Mount Cylinder Choke Tube Specifications Manufacturer: Carlsons Model: Tubes Flush Mount Cylinder Choke Tube Gauge: 20 GA Choke Constriction: Cylinder Mount Type: Flush Thread Pattern: Invector Bore Diameter: .620 Material: Stainless Steel Compatible Hosts: Winchester Mossberg 500 Browning Invector Weatherby Savage Shot Compatibility: Steel Lead Copper Plated Nickel Hevi-Shot Bismuth Available At: GrabAGun