Kimdrox 2 Wires Small Digital Voltmeter Power Volt Meter 0.40" Waterproof Battery Monitor 12 Volt Panel 3.0-30V DC Auto Gauge Blue LED Display Ultra-small size(402523mm), 2-wire simple connection, handy and easy to use. Wide voltage measuring range: DC3-30V; Max voltage input: DC30V. Simply connect the red and black wire to positive and negative pole of measured voltage respectively Reversed connection protection prevents the meter from being burn when wires are connected reversely Moisture-proof, anti-oil, anti-vibration and waterproof(please do not merge the meter in water