Patternmaster CODE BLACK TIMBER tubes will extend out the end of your barrel about 3/8 of an inch and has an effective range of 15 to 40 yards. You will see a pattern similar to an Improved Cylinder constriction choke on paper, 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 TIMBER tubes can be used with steel or other non-toxic ammunition as well as lead, and with 2 ¾" or 3" shells. Pick your favorite shot size to use which can range from 8 to BB Non-Toxic/Steel and Lead 8 to 00 Buck. CODE BLACK TIMBER tubes only come in a Non-Reflective Bronze color and are not ported but have a knurled end for hand tightening. Note: Testing done by Ballistics Performance has determined that ammunition with velocity of 1550fps and below will achieve the best results with Patternmaster Tubes.