Using this digital angle protractor, you can measure the angle between two , not only in earth direction. Angle key at the first face, and then rotate slowly and must keep the rotation to another testing face, It then show the angle once you not move the unit. Any angle measurement is using gyro technique. High accuracy ±0.05°, high resolution 0.01°. Li- battery rechargeable, . High resolution, professional measurement. Single and dual , convenient to measure the angle. Dual and single with user friendly LCD display angle. V shape case for easy to fit at the corner or pipe. With 5 Side Magnetic base, audible alarming at settable angle range, any angle measurement. The unit could be by connecting the USB cable to the unit and a computer's USB port. Accuracy: 0 to 20°: ± (0.05°) 20 to 70°: ± (0.1°) 70 to 90°: ± (0.05°) Measuring Range Single : 360°,Dual : ±40° Resolution: 0.01° Response Time: Less than 0.4 second Zero Offset Drift Angle Per ℃: 0.0058°(typical) Operating Temperature: 0 to 50℃(32 to 122℉) Storage Temperature: -10 to 60℃(14 to 140℉) User Interface: Mono-color LCD with backlight Supply Power: Rechargeable Li-Polymer 3.7V Charger Port: 5V 500mA Mini type-B USB port Power Consumption: tandby: 10uA, Operation: 20mA Standby Battery Life: 4000 hours Operating Battery Life: 40 hours Magnetic Base: Set on 4 corners Magnetic Force: N48 Item Size: 7x7x2.8cm/2.7x2.7x1.1in Item Weight: 119.7g/4.2oz Colour:As Shown Material:plastic Package Contents: 1 * Dual Digital Angle Protractor Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.