Our Sporting Clays Choke Tubes are made from 17-4 stainless and precision machined to produce a choke tube that patterns better than standard choke tubes. These choke tubes feature a 25% larger parallel section in the choke thus throwing more consistent patterns than conventional choke tubes. Each choke tube is knurled on the end to allow for quick and easy removal. Each choke tube has the constriction laser marked on the end for easy reference. These choke tubes are backed by our lifetime warranty. – Lead shot Steel Shot Copperplated Shot Nickel Shot Hevi-Shotshells™ and Buck Shot can be used in our Sporting Clay Choke Tubes. Steel shot larger than BB should not be used in any Sporting Clays Choke Tube tighter than Full Constriction. Our Sporting Clays Choke Tubes will throw tighter/denser patterns than Flush Mount Choke Tubes due to a longer parallel section. – Fits Browning Invector-DS 12 gauge Choke System