VvW 2 Wire Green LED Panel LED Display Voltage Meter Voltmeter+with Reverse Polarity Protection+waterproof With Reverse polarity protection,Brand new and high quality.Measuring Range: DC4.0-30V Minimum input: DC4.5(Below this voltage,it will show measurement inaccurate, or don't show). Maximum Input: DC30V(please do not exceed 30V, otherwise, the meter would be damaged.). Refresh speed: about 500ms/each time. Size:4.8cm x 3cm x 2.2cm - 1.89inch x 1.18inch x 0.87inch