Universal Pen turning Bushing

Well, mostly universal. The hole is 7mm to fit on standard mandrels then it steps up 8mm, 9mm, 10mm, 11mm, 12mm, and the top is 13mm. So the largest blank you could put on is 12mm.

The bushing does not actually serve as a guide to show you how deep to cut, but can be used to estimate if your final size matches a level of the steps. I use calipers.