This is a HSS hand or power reamer, just the right size for cleaning up those nasty dents in those German foil barrels.
This reamer should only be used on German Foil Barrels: Standard, Extra, Belgian and V2A. It is fine on all FWF - Uhlmann and Allstar barrels for foil.
Does not fit a "French" foil barrels, unless you want a mess on your hands.
For those asking the BIG question: it is 4.5mm or .1772" with a male end
There is a sharp point on the end of the reamer so that the tip will hit the center of the brass hat in the cup and will not allow the reamer to cut any of the plastic cup away or damage the cup. Smart?