The Carlson's 20 Gauge Winchester Flush Mount Choke Tubes have been molded from 17-4 stainless steel and then hardened to ensure a durable and long lasting product. These Choke Tubes built by Carlsons Choke Tubes are ideal for use with lead shot in all constriction sizes. The 20 Gauge Flush Mount Choke for Winchester by Carlsons is the perfect tool for any shooter whose grouping patterns are lacking in tightness. This Carlsons Shotgun Choke has an end that is knurled for easy removal and has a constriction type etched on the side for reference in the field. Interchangeable with Winchester Mossberg Browning Invector Weatherby and Savage 12 gauge & 20 gauge shotguns Knurled end for simple installation Constriction is marked on the side for reference