DROK Digital Automotive Voltmeter DC 3-30.00V 12/24V Car Battery Condition Gauge Blue LED Display Measure Range: DC 0-30.00V; Accuracy: 0.02V; Refresh rate: about 300mS / times; Power Supply: DC 7-28V Display: 4 digits 0.36" LED Tube Anti-reverse protection: over-range display "0" Dimensions: 40.5mm x 24mm x 17.5mm