Digital Ruler and Protractor: A ruler with digital protractor function that can measure length and angle at the same time. Say goodbye to complicated measuring or tracking tasks. Metric and Imperial: length measurement from 0 to 400 mm (7 inches on both rulers). The angle measurement range is 000.0 to 999.9, and the scale can be rotated more than 2 turns. Resolution 0.1; Accuracy 0.3. Zero any position (tare): Press and hold 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. The big button in the center of rotation locks/unlocks the ruler at any angle, avoiding misaligned or lost measuring angles. SIMPLE BUT DURABLE: Simple in design, but made of stainless steel, this high-end material ensures excellent sturdiness. Button battery life is more than 2000 hours, solving all duration problems battery life.