Needed a concentricity checker so went out in my shop and dug around for parts...actually had to buy the (skateboard) bearings to use, but most of it came from my shop and then a little imagination and a little bit of work on the milling machine.... here are some pics...it is good for carious calibers and also adjustable to take measurements at various distances from the case head . If you want to ask any questions, drop me a note!