Reed TM-8811 Ultrasonic Thickness Gauge has a micro-computer LSI circuit & crystal time base and provides a high accuracy of 0.5% + 0.1mm. Units digital display provides exact readings, while the broad band receiving sensitivity means it can read probes of different frequencies. Product also provides auto calibration, automatic material calibration, metric or imperial selectable, as well as the option to display sound velocity at the touch of a button. Units measurement ranges: 1.5 to 200 mm (#45 steel) and velocity: 500 to 9000 m/s. The ultrasonic thickness gauge measures the thickness of steel, cast iron, aluminum, red copper, zinc, quartz glass, polyethylene, PVC, gray cast iron & nodular cast iron.