Carlsons 07775 Delta Waterfowl Retay 12 Gauge Mid-Range 17-4 Stainless Steel Black These choke tubes feature a longer parallel section allowing for fewer flyers and denser patterns. These choke tubes extend 3/4 " outside the barrel eliminating damage to your barrel caused by prolonged steel shot use. The longer parallel section allows for use of larger steel shot in tighter choke constrictions. They are made of 17-4 stainless with a knurled extension and a blue finish. All steel shot sizes may be used in the close and mid-range choke tubes.