Im looking for a concentricity gage and this seems to be a pretty handy device. Since I don't have a very high end press (Hornady Lock-N-Load) but I am using Redding dies I am quite sure that my reloads have a certain amount of runout. Currently I am only shooting an AR so extreme accuracy isn't too important but when I get my custom .308 bolt gun built this month I will definitely care more about consistency and decreasing run out.