Patternmaster's CODE BLACK DUCK tubes will extend out the end of your barrel 1 inch and has an effective range out to 60 yards. You will see a pattern similar to a Full constriction choke on paper with a 2 ¾" or 3" shell and a Modified with a 3 ½" shell, but because of the patented "stud ring" inside the tube, there is a much shorter shot string. This shorter shot string will allow more shot on target all at once so your down range energy is sure to kill instead of cripple. Our CODE BLACK DUCK tube can be used with steel or other non-toxic ammunition as well as lead, 2 ¾" or 3" or 3 ½" shells. Pick your favorite shot size to use which can range from 8 to BB Non-Toxic/Steel and Lead 8 to 000 Buck. CODE BLACK DUCK tubes only come in a Non-Reflective Bronze titanium coating and are ported. Patternmaster tubes are made of Carpenter Custom 630 (aircraft quality) 17-4ph stainless steel and are heat treated to the optimum level for best performance.