The principles of air gaging are straightforward yet effective: compressed air is blown through opposing jets across the diameter of a bore, causing a drop in upstream back-pressure as the bore size increases. This creates a pressure-distance curve in a precisely configured system.

Air gaging, one of the earliest forms of precision measurement, has been used in industry since the 1930s. It was the first technology available for extremely close tolerance measurements, and many of the air plug configurations developed in those early days have remained largely unchanged.