[NOTE] PLEASE MANUALLY CALIBRATE BEFORE USE. How to calibrate? Please refer to the video or user manual. [Calibratable] Before measurement,it can ensure a measurement accuracy of plus or minus 0.05° after manual calibration. [Wide Measurement Range,High Accuracy&Two Types Readings] This digital level box can measure angles up to 4 × 90° or 2 × 180°,measurement resolution 0.05°,accuracy ±(0.5°+ 5 digits),providing two types readings-angle and slope. [Absolute Angle Measurement Mode&Relative Angle Measurement Mode] The digital protractor can measure the angle between the measured surface and the horizontal plane,record the angle at the starting position, and measure relative to this starting position in subsequent measurements.In addition,it can also calculate the slope. [2 Sides with Infrared Rays] Built in infrared emitters on both sides can emit two infrared rays as a reference for angle measurement. [1.90” LCD Screen Displaying with Green Backlight&Displaying Reverse Automatically] The LCD screen will display the readings in real-time,you can see them clearly from any angle without reflection or glare and the display will reverse automatically on the screen,so it’s easy to read. [4PCS Magnets Are Built into The Bottom,Top and 2 Sides] The 4PCS magnets are built into the bottom,top and two sides respectively,making it more convenient and efficient to use. [Rechargeable] Its power source by the built-in the 320mAh/3.7V rechargeable battery.