HeviShot Combo 12 Gauge Waterfowl Choke Tubes have been built to put maximum lethal pellets on your waterfowl. These chokes features a ported, knurled fore end for easy installation in the field under any condition, without tools. The porting drops gas pressure at the muzzle, helping ease the wad away from the shot, reduced recoil, and dampen muzzle jump. The choke tubes feature internal axial rings to keep the shot cloud on target. The tubes are formed from aircraft stainless steel for years of carefree use, and finish in matte black for concealment. These combo choke tubes include mid range choke for shooting over decoys or in flooded timber and extremem range choke for shooting going away, long shot bird. You can have both applications with the Hevi-ShotCombo 12 Gauge Waterfowl Choke Tubes. A sweet system!