SMAKN&reg; 0.28" Micro Waterproof Dc 3.50-30.0v 2-wire Led Digital Voltmeter Dislpaly Volt Panel Meter Voltage Tester Gauge Monitor (Red) Dimensions: 27mm * 15mm * 18mm (with fixed ear size) Range : DC3.50-30.0V Display: three digits 0.28-inch LED digital tube Refresh rate: 1s /time Measurement accuracy: 1% (+ / - 1 words)