Air Plug Gauges

Air plug gauges are precision instruments used for measuring internal diameters of cylindrical parts. These gauges use air pressure to determine the bore size, taper, and ovality of the part being measured. The image shows two types of air plug gauges: one with a larger base and multiple adjustment knobs, and another with a smaller base and a simpler design. The gauge on the left, the Mahr Marstand 820 NC, has a more complex structure with multiple adjustment knobs, while the one on the right has a simpler design with fewer controls.