The Diamond Tool Holder is available in five sizes, from 8mm - 16mm tool height.
The original design for the tool meant that the shank had to be angled at 12 degrees so that it could slide and surface at the same setting. This design is a compromise to make the tool easier to use when screwcutting, so that the shank doesn't get in the way as much when cutting a thread close to the chuck. See the images below for more detail.
The 8mm, 9.5mm, and 12mm tools have been redesigned so that the tool tip can face and surface when the shank is at 90 degrees to the mandrel. This makes the tool much more convenient to set up when used in a quick change or 4-way tool post. The 8mm, 9.5mm, and 12mm tools are also available in a left hand version for cutting towards the tailstock and left hand shoulders. The left hand tool also gets around the problem of the shank getting in the way of the chuck when cutting threads.
To select the correct size tool holder for your lathe, take a measurement from the base of the tool post where the holder will sit on, to the centre height line of the lathe.
This measurement is the lowest practical setting that the tool bit should go down to, but the tool tip can be moved up or down for fine adjustment to get the point on centre. Of course you can always put a piece of packing under the holder to bring it up higher for a bigger lathe.
If you are using an adjustable tool post, set it close to its lowest point before measuring.
Once you have decided which tool holder is best for your lathe, use the online shop to purchase.