Carlson�s Ported Bone Collector Turkey Choke Tubes feature a super tight, pattern tested constriction that throws extremely tight patterns with all shotshell ammunition loaded for turkey hunting including lead, nickel-plated, copperplated, bismuth, hevi-shot, tungsten, and TSS. A longer taper section to the constriction (parallel section of choke tube) insure tight patterns with less flyers.� More pellets on target every shot! �The Bone Collector Choke tubes are precision-machined from 17-4 heat treated stainless steel and feature a non-reflective matte black finish. Each choke tube constriction has been pattern tested and has thrown the best patterns with 4 through 10 shot. If you wish to use shot size�s larger than #4 shot, use a more open choke tube for optimum patterning.