Improves the accuracy of cast and jacketed bullet reloads. Doesn't stretch cases like standard expander button style dies do. Works in a two step process, the first step expands the inside of the case neck to just under bullet diameter. The second step expands the case mouth to bullet diameter or slightly over so that the bullet can be started perfectly centered. Notes: M-Die expands the case neck to just under bullet diameter for precise neck tension in first step. Second step flares case mouth to bullet diameter or slightly over for proper seating.