For motors, fans, etc. When a reflector is attached to the rotor blade, for example, the revs are counted using a laser, without physical contact. Reflector tape is included. Measuring range 2-99999 rpm. Measuring distance 50-500 mm. Accuracy ±0.05% + 1 digit. Large, clear LCD display. Memory for max, min and latest readings. Operates on a 9 V battery (included) or 6 V adaptor (not included). Size: 160x58x39 mm. Comes with storage case.