Features:
Dual USB ports support 5V 4.2A output. Can charge two devices at the same time. Including: Apple iPhone, Blackberry, Garmin GPS, Droid, Samsung, HTC EVO, GoPro Hero, GoPro Hero3 and Vholdr helmet cams.
LED voltage meter will show the voltage when powered. It can monitor the battery in case of unusual condition.
CE and Rohs approved. With overload, over current and short circuit protection.
With high-grade ABS material and sealed by ultrasonic. The case has high temperature and corrosion resistant.
Waterproof cap to cover the USB ports when not using.
NOTE:The voltage reading will be visible only by connecting to the battery and the voltage also can be read when the cover is engaged.

Specifications:
Color: Black
Material: Copper + ABS Plastic
Product Weight: 40g
Input Voltage: 12V - 24V
Output Voltage: 5V ± 0.25V (USB x 2)
Output Current: 2 * 2.1A max.
Voltage Display Range: 0V - 24V
Dimension: about 7.03 * 4.36 * 3.44 cm
Multi-purposes: supply power for cellphone, tablet, GPS and other USB-devices

What's included:
1Pcs Dual USB with Voltmeter Adapter