Occasionally I like to use my laptop in the car, mostly connected to a wifi hotspot and try to get some work done while my wife drives.  Unfortunately my laptop is a few years old and can only do a few hours on battery, which means I need to plug it in.  Previously I had used 400+ watt inverters, which worked fine, but took up a lot of space, and were quite loud.  This inverter is a lot smaller in terms of capacity, but it offers enough for most laptops out there, it's also near silent.I questioned it being able to fit into a cup holder, not sure that I wanted the power cords all going up to the center of the car instead of a mess of cables on the floor.  Turns out it provides two nice things, one because there is usually a 12V receptacle near the cup holders, this means it has a nice and short cord.  The other is that it fits into the cup holder which means it's not rolling around, it stays nice and secure.  It didn't fit perfectly into our 2004 Pontiac Grand Prix cup holder, not being able to go all the way to the bottom, but still is secure enough.Having 4 USB ports seems a bit overkill, but seeing as how almost everything charges or runs off of usb, it's probably a great thing.  It provides the hard to find 2.1amps (which means you can charge your full size iPads while still powering them), however it is shared across all 4 USB ports.  What this means is that if you have two power hungry retina 10" iPads you won't be able to charge them both at full speed.  Probably not a concern for most people, and having 2.1amps is great since it is much much faster instead of just staving off an empty battery.The only minor gripe is that with the MacBook Air's wall art (without the extension), it covers up a few of the usb ports.  I would assume this is true of the larger MacBook Pro (and retina) power adapters as well.  It's not a huge deal, if you have a thin usb cable head it might still work, and the ones on the side should still work.  Otherwise just make sure to test fit it and bring the extension if necessary.Overall this is a very compact unit, it's almost dead silent, it provides USB (and 2.1!) charging.  The new generation of laptops are providing enough battery life for a days work and then some, but for everyone else, this is a great way to give yourself a boost on the go.