REED Instruments TM-8811 Ultrasonic Thickness Gauge, 7.9" (200mm) Measures the thickness of steel, cast iron, aluminum, red copper, zinc, quartz glass, polyethylene, PVC, grey cast iron and nodular cast iron Quick responding and high accuracy with large LCD display Automatic material calibration User selectable unit of measure (in/mm) Includes ultrasonic couplant gel, probe, hard carrying case and batteries