These DAR-200 Carbatec Digital Angle Rulers offer a way to measure angles quickly, easily & with outstanding accuracy. When open they are 400mm in length & when folded they are 200mm. They capable of measuring from 0 degree to 360 degrees in 0.1 degree increments. The digital display can be zeroed at any degree giving you the ability to measure between specific angles. Once you reach your desired angle you can use the mechanical lock to prevent movement.