Ultrasonic Thickness Gauge 1,measuring metal :steel, cast iron, aluminum, copper... 2,Measurement Range: (0.75 ~ 300) ... Ultrasonic Thickness Gauge1. Suitable for measuring metal (such as steel, cast iron, aluminum, copper, etc.), plastic, ceramic, glass, glass fiber ... optional) Operating voltage: 3V (2 AA size alkaline batteries)Continuous working time: more than 100h (not open backlight pm) ...