Special field-tested constriction for optimal performance; Designed for Winchester Blind Side 2 Ammunition; Compatible with HEX Steel Shot and Diamond Cut Wad; Delivers devastating downrange patterns; Performs well with other steel shot loads and over extended distances; Suitable for lead, plated copper, nickel shot, and Hevi-Shot ammunition; Mid-Range model compatible with all steel shot ammunition; Extended Range model not recommended for steel shot larger than BB or faster than 1550 fps