Digital protractor ruler: A ruler with a digital protractor function, capable of measuring length and angle simultaneously. Say goodbye to complicated measuring and drawing.Metric and Imperial System: Length measurement range 0 to 400 mm (both rulers are 7 inches long). Angle measurement range 000.0° to 999.9°, the ruler can be rotated more than 2 full turns. Resolution 0.1°; accuracy ±0.3°.Zeroing at any position (tare): Press the small zero button for one second; the value on the angle display will be reset to zero, and you can start measuring at any angle. Turn the large knob in the center to lock/unlock.the ruler at any angle, to avoid any displacement or loss of the measured angle.Simple yet durable: Simple design, but made of stainless steel, an excellent material ensuring exceptional strength. The button cell battery lasts for over 2000 hours, eliminating any concerns about battery life.