Carlson's CrematorA(R) Choke Tubes feature these brand new Triple Shot Technology (TST) and is offered in close mid and long range constrictions. TST is a series of three graduated rings in the taper section of the choke tube that allows a more gradual transition from the shotgun bore to the final constriction.This design offers reduced pellet deformation, less flyers and more dense patterns. These benefits make the CrematorA(R) Series extremely effective on all types of waterfowl throughout the entire season. Mfg: Carlsons