Interapid 01639023 (formerly 01690032) shown above (indicator not included)
For hassle free precision measuring, a high quality magnetic base is indispensable.
These Swiss-made magnetic bases, with fine adjustment, are the highest quality you're likely to find. They're sturdy enough so that you can use them with high resolution test indicators (.0001" or 0,002 mm for example).
The clamp will accommodate the 8 mm diameter stem of dial indicators (as shown in the photo above) and the stand is ideal for electronic probes as well. (It will not be possible to mount indicators with 3/8" diameter stems.)
The 11" long reticulating arm can take on numerous configurations and one knob tightens everything securely into place. At that point you can use the fine adjustment knob located on the clamp, to get your indicator or probe into position.
The end of the arm accepts any brand test indicator dovetail, but you'll probably want to use this magnetic base with other high quality instruments made in Switzerland, such as Interapid, Compac, Tesatast or Bestest indicators.
This close-up of the clamping mechanism shows a Compac indicator held by the dovetail. The black knob tightens the clamp onto the dovetail while the metallic knob allows for fine adjustment of the indicator's position after everything else is set in place.