Precision diameter tapes are used for measuring the true diameters of both round and out-of-round forms. Used in the metalworking industry, these tapes are precision tools made of 1095 clock spring steel.

The precision-diameter gages consist of a narrow metal ribbon bearing special graduations. These graduations are designed to convert circumferential distance into diameter measurement so the observer can read the diameter directly from the scale.

The tapes are checked over master gages at 0.001 in (0.025 mm) accuracy for standard tapes up to 144 inches (3,658 mm).