Carlson's Choke Tubes 07255 Delta Waterfowl Extended Choke Remington Rem Choke 20 Gauge Mid-Range 17-4 Stainless SteelCarlson's Delta Waterfowl Extended Choke Tubes are manufactured from 1704 stainless steel and designed to throw tighter and denser patterns than conventional choke tubes. These choke tubes feature a 25% longer parallel section in the choke, thus throwing more consistent patterns. Each choke tube is knurled on the end to allow for quick and easy removal. Each choke tube has the constriction and size laser marked on the end and body for easy reference.