Combination Voltmeter, USB Charger and Power Switch. Draws no power when off. Motorcycles, indoor or outdoor RV mount, marine applications. #CSVU-B/SW The on/off switch turns the power off to the device when not in use. The snap over waterproof front cap is translucent so you can see if the device is on or off with the cap on. The digital voltmeter comes in blue and is available in red, reads to 30 VDC. The USB charger is a powerful output equivalent to factory supplied chargers for most cell phone manufactures. Mounts in panels up to 1-1/4" thick in a 1.128 inch hole with the backing nut. Comes with a rubber mounting washer that can be used to seal the front mount or can be used as a locking washer with the nut for high vibration applications.