Features: Voltage Frequency Meter AC 50-500V LED display of AC voltage and frequency in the same for time. Frequency range: AC 10.0-99.9HZ ,auxiliary power: 2 wires AC50-500V. The data is more intuitive, LED two-color display, red + green, clear and easy for monitoring at a glance. This Voltage Frequency Meter is easy to install, embedded installation, more stable. Meter only fits with pure AC 50-60HZ power supply, not be used for square wave, inverter output. Specifications: Material: Plastic Size: 70x40x25mm/2.7x1.6x1.0in Measuring range: AC 50-500V, AC 10.0-99.9HZ Power supply: 2 wires AC50-500V Note: Please allow 1-3cm error due to manual measurement. pls make sure you do not mind before you bid. Due to the difference between different monitors, the picture may not reflect the actual color of the item. Package includes: 1X Voltage Frequency Meter