This is a high quality Vector Products 500 watt inverter. If you happen to be out in the boonies and need 120 volt AC power for say a little refridgerator you could either hook this thing directly to a battery or plug it into the power port on your rig and like magic you have 500 watts of alternating current (AC for short). Powers up to 4.2 amps. Also has a USB port if you need to charge your phone.
This inverter is rated for 500 watt continuous and 1000 watt of surge. Don't look at those cheap units that claim they are the bomb, they might claim 500 watt but also check the surge rating, this is the starting current that occurs with almost all devices and separates the wheat from the chaff on these inverters so to speak. This is a nice size that you could throw in your rig.