Glenn; A mandrel is one way of turning. Turning between centers is another way and requires no mandrel, and on a single barrel pen, no bushings, just a 60 degree live center for your tailstock, and a 60 degree drive for your headstock. One setup will fit all size tubes. Turning between centers is the way one would normaly run a lathe unless you were turning something with an open end. When you get more advanced in pen turning and do custom or closed end pens you will not be able to use a mandrel. So, if you want to learn to turn between centers to begin with, you can save a lot of money by not having to purchase bushings for each different kit. There are several good hints and tips on how to turn between centers on this sites library. If you have questions, just ask, someone will have an answer here for you. Jim S