Made out of surgical grade stainless steel. Can be used to measure internal, external and height dimensions with extreme accurately.Linear capacitive measuring system. Large, Clear Digital Readout. Can be set to zero setting at any position within measuring range. With a small locking thumb screw which locks the jaws in place. Very handy conversion chart at the back. Very Slim & Lightweight so easy to carry anywhere. One button changes unit from Metric to Inch and vice versa (true measurement, not calculated). Measure not only thickness, plus inner width, stepping, differential, and depth up to 6 inch. Not to be confused with the smaller version. This is for professional use.