Measures banjo head tension directly from the head for accurate tap-tuning. Sits on the head, backlit digital display. Included edge guide ensures that it is always the same distance from the tension hoop for accurate reading. Comes with clear instructions, glass square to use in calibration, foam-padded plastic carrying box. One year warranty. More accurate than a torque wrench which measures bracket tension. Display powered by a 3V Lithium battery (CR2032, included).