Features: 1. Auto calibration to assure the accuracy. 2. Sound velocity measurement: with a given thickness to measure the sound velocity to improve accuracy. 3. Preset 12 sound velocities for different material. 4. Coupling status indication, thickness alarm setup, backlight display, low battery indication and auto power off function. 5. 12 kinds thickness measurement data store and recall. 6. Metric/Imperial can be selected. Specification: Condition: 100% Brand New Model: GM130 Measuring Range: 1.00-300.0mm(steel) Accuracy: ±(1%H+0.1mm) H denotes the measured thickness Working Frequency: 5MHz Resolution: 0.01mm(1.00 to 99.99mm), 0.1mm(100 to 300.0mm) Minimum Limit for Tube Measuring(steel): 15*2.0mm, 20*3.0mm Sound Velocity Range: 1000-9999m/s Thickness: ≤20mm, accuracy of velocity: ±1% Operating Environment: Operating Temperature: 0-40° Temperature of Workpiece: <60° Relative Humidity: <90% Power Supply: 3 * 1.5V AAA Battery(not included) Operation Current :≤35mA(with back light on) Weight: Approx. 1070g / 37.7oz Size: Approx. 155 * 78 * 33mm / 6.1 * 3.1 * 1.3in Package List: 1 * Thickness Gauge 1 * Dia.10 Transducer(5KHz) 1 * Dia.6 Transducer(5KHz) 1 * 4mm Sample Block 1 * Carry Box