Inside calipers are used for taking a measurement where rulers or digital calipers will not fit or reach. Reach inside the object and set the inside calipers to the distance to be measured, then remove them from the object and measure across the tips with a ruler or digital calipers.

The separate hub ensures that the legs pivot on the large diameter, smooth hub rather than the small diameter, threaded central screw. This gives greater accuracy. It also ensures the screw does not tend to loosen, because the screw and nut do not move relative to the hub. The slightly angled surface on the bottom of the two hub parts stop them rotating when they are fitted together.

Print two legs and two hubs. Secure with one M3 6mm DIN912 machine screw and M3 nut.

These are styled after McMaster part number 1962A31, so if you like these but want something more rigid and durable, those are the ones to get.