Carlson's Choke Tubes are manufactured from corrosion resistant 17-4 PH Stainless Steel. Carlson's Extended Super Steel Choke Tubes are designed specifically for steel shot. They feature a longer parallel section which creates a denser pattern and reduces the occasional flier. The Extended Super Steel Choke Tube extends 3/4" outside the barrel which eliminates damage to the barrel caused by prolonged steel shot use, they feature a knurled extension, blue finish and are backed with a lifetime warranty. Extended Steel Shot Choke Tubes pattern best when using steel shot and typically throw a pattern that is 10-15% more dense than flush mount choke tubes.