I bought mine with an integral R8 shank to fit my milling machine. It's probably very slightly less rigid than using R8 collets, but it sure is a whole lot faster, easier and more convenient because both your hands are at the tool while changing, rather than one hand holding the tool while the other loosens the drawbar at the top of the headstock. Mine was beautifully finished with very little runout. Came with a real nice spanner too, but it's so easy to use and the knurling is so nice, that I've never used it yet. If you work on big parts and need lots of vertical clearance on your milling table, you may want to go with the R8 collets. But if your work is mostly small to medium parts, then this would fit the bill perfectly.