Made from 17-4 stainless steel; 25% longer parallel section for more consistent patterns; Knurled end for easy removal and installation; Constriction lasered on the end for quick reference; Compatible with Lead, Copperplated, Nickel, Hevi-Shot, Bismuth, Tungsten, and Steel shot; Restrictions: No Steel shot larger than BB or faster than 1550 FPS in Full or EF constrictions; Backed by a lifetime warranty