【Measure 360° and Hold Data】Protractor measuring range: 0-999.9°; Resolution: 0.05°(3'); Accuracy: ±0.5°; The goniometer, can measure 360° interior and exterior angles, supports degree and degree/minute unit conversion. It has hold button and zero button. To lock the data, please press the HOLD button. (Turning the knob is only for loosening and tightening, cannot completely fix the angle) 【4 in 1 Multifunctional Digital Protractor】: This product is a combination of protractor, spirit level, circular spirit level and ruler. It is calibrated by 3 spirit levels. Help you better measure the angle. (NOTE: This is NOT a digital level, no number is displayed on the LCD screen, can only judge whether the object is tilted). The main ruler is a dual scale in metric and inch. 【Large LCD Screen & Auto Power Off】: This protractor has a large full-screen LCD screen that allows you to read the data easily and quickly. The digital angle ruler will automatically turn off after 5 minutes of inactivity