TensionRite Belt Frequency Meter Includes (4) AA Batteries Calibration Tuning Fork Protective Case Features Direct Rather Than Indirect Measurement of Vibration Frequency Meter Range Matches inReal Life in Belt Installation Parameters Quartz Crystal Based Solid-State Circuitry For Belt Series TensionRite For Belt Trade Size All Belt Sizes Includes Batteries Yes Power Source Battery Product Type Belt Frequency Meter Testing Tool Material Aluminum Units of Measurement Hertz