Ultrasonic thickness gauges operate on the pulse-echo principle. The probe transmits ultrasonic pulses into the material; reflections from internal interfaces are received, and the time of flight is precisely measured to determine material thickness. These instruments are suitable for thickness measurement of metals (e.g., steel, cast iron, aluminum, copper) and non-metallic materials such as plastics, ceramics, glass, and fiberglass with good ultrasonic transmission properties. Typical applications include petrochemical, automotive manufacturing, shipbuilding, aerospace, rail transit, metallurgy, machining, and the inspection of pressure vessels and pipelines.