Hornady Lock-N-Load Concentricity Tool. This tool identifies and eliminates bullet runout (or wobble). Just place ammunition in the tool, roll it, identify runout and use the dial indicator thumbscrew to adjust. Features Universal centers ensure precise alignment of most bottleneck cartridges from 22 cal up to 45 cal. Easy-to-use precision adjustment knobs allow you to true up the runout on any cartridge. Sturdy frame can be bolted to your bench Provides improved accuracy for hand loaders, and can be used to true up factory ammo too.