The Hornady Lock-N-Load Ammunition Concentricity Tool is just what you need to prevent bullet run out from ever becoming a problem again. This revolutionary tool is the first of its kind on the market, proven to identify and to abolish bullet run out. To use the Hornady Lock-N-Load Ammunition Concentricity Tool, all you have to do it place your chosen ammunition in the tool, then roll it, identify any bullet run out, then use the included dial indicator to adjust the bullet run out back to zero. This tool is highly effective and easy to use