A self-leveling line laser with an accuracy of 0.30 mm/m (often specified as 0.3 mm/m) is a high-precision tool used for indoor and light commercial alignment, hanging, and layout tasks. The "0.30 mm/m" rating means the projected laser line will drift by no more than 0.3 millimeters over a distance of one meter (achieving about ± 3 mm over 10 meters),