Carlsons 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 sizes larger than #4 shot, use a more open choke tube for optimum patterning.Remember to pattern your shotgun choke tube with the specific shot shell load you are going to be using.Different types and manufacturers of ammunition will throw different patterns from the same choke tube.Gauge: 20 GaugeConstriction Type: TurkeyConfiguration: Benelli Crio PlusFinish: Matte BlackConstrictiondiameter: .565Material: 17-4 Stainless Steel