Using this digital angle protractor, you can measure the angle between two faces, not only in earth  direction. Press Angle at the first face, and then rotate slowly and keep the rotation to another testing face, It will then show the angle once you not move the unit. Any angle measurement is using gyro technique. 

Features:
High accuracy ±0.05°, high resolution 0.01°.
Li-lon rechargeable, .
High resolution, professional measurement.
and dual , convenient to measure the angle.
Dual and with user friendly LCD display angle.
V shape for easy to fit at the corner or .
With 5 Side base, audible alarming at settable angle , any angle measurement.
The unit could be charged by connecting the USB cable to the unit and a 's USB port.

Specifications:
Color: Red
Accuracy:
0 to 20°: ± (0.05°) 
20 to 70°: ± (0.1°) 
70 to 90°: ± (0.05°) 
Measuring : 360° , Dual : ±40° 
Resolution: 0.01° 
Response : <0.4 second
Offset Drift Angle Per °C: 0.0058°(typical) 
Operating : 0 to 50°C (32 to 122℉)
Storage : -10 to 60°C (14 to 140℉)
User Interface: Mono-color LCD with backlight 
: Rechargeable Li-Polymer 3.7V 
Port: 5V 500mA type-B USB port 
Consumption: tandby: 10uA, Operation: 20mA 
Standby : 4000 hours 
Operating : 40 hours 
Base: Set on 4 corners 
: N48 
Item Size: Approx 7 * 7 * 2.8cm / 2.7 * 2.7 * 1.1in
Item Weight: Approx 119.7g / 4.2oz
Package Size: Approx 12.5 * 10 * 5.5cm / 4.92 * 3.94 * 2.16in
Package Weight: Approx 270g / 9.5oz

Package List: E0916-USB
1 * Digital Angle Protractor
1 * USB Cable
1 * Storage Bag
1 * User Manual