Double USB with Digital Battery Volt & Amp Meter with Double Black Face PlateDouble USBSize 42mm diameter12vcompatibleDual USB sockets2.1A / 1A ratingFlip down waterproof coverThis compact 12v double USB socket is easy to install and provides convenient 12v charging facilities for items such as phones and tablets. Ideal for day vans and smaller campervans where space is of a premium.These sockets are also used in vans, MPVs and cars to provide a useful USB power source. Simply wire to your main vehicle battery, or leisure battery via a 10amp fuse.Volt & Amp MeterThese compact unit differs from most in that it measures both voltage and current (amps). The voltage measures the health of your leisure battery. Whereas the current reading (amps) measures the flow of power along your cable to your appliances. If you want to work out how much power in watts is being drawn by your appliance, then you can use the equation:W (watts) = V (volts) x A (Amps). For example, if the Ammeter is reading 4 amps then the power consumption would be 12 Volts x 4 amps 48 watts.This unit can also be used to gauge how much power in amps is being pushed into your battery by your solar panel, this is very useful to know as it will give you an idea on how fast your leisure batteries are being charged.Operating voltage DC 12v-24vMeasurable voltage DC 6-28vMeasurable current 0-10 ampsMaximum input Dc 20amps