I was looking into getting pin gauges to measure various holes eg. each chamber in a revolver cylinder to calculate the correct sizing for cast bullets - but pin gauges are a bit of a pain to assemble one-by-one from MSC or whomever and I happy discovered 'Small Hole Gauges' instead:
Pretty cool - inexpensive around $16 for the set and very handy. As you might tell from the pic, each one is adjustable by dialing the knob at the end which retracts the center piece and thereby expands the ball while inside a hole - then pull the ball out and measure with calipers or micrometer.
Far less expensive and fiddly than pin gauges.
