This accessory to the concentricity tool offers the next step in ultra-precision reloading. Its .0005 increment dial indicator helps identify neck thickness variations so you can sort and measure case necks or verify your neck turning operation ultimately Enhancing accuracy. (Concentricity tool not included.) features:- 1: 22 Cal .224" - 3: 6mm .243" - 4: 25 Cal .257" - 5: 6.5mm .264" - 6: 270 Cal .277" - 7: 7mm .284" - 9: 30 Cal .308" - 13: 338 Cal .338" - 15: 35 Cal .358" - 19: 45 Cal .452"