CandyQ DC-DC Buck Voltage Converter 4.5-40V 12V to 5V/2A Step-down Volt Transformer Stabilizer Voltage Regulator Module Power Supply Switch Inverter Board with LED Voltmeter 5V USB Charger Integrated voltmeter, buck voltage converter and 5V USB charger port, multifunctional and practical. Wide voltage measuring /input range: DC 4.5-40V; with self calibration, high accuracy. Output Enable" button for usb output and "low power" button for low power-consumption mode. With reverse connection, over-current and over-temperature protection, hence safe for use. With LED indicator for USB power supply and wiring terminals, easy and convenient operation.