I bought the Juice Cube simply out of convenience. It was about £25, and is compatible with most devices. Not the Iphone 5 though. For whatever reason they've not made a bit for that - I take my usual cable with me as that does the job.
I really like my little pink charge - it can get me from 3% to about 80% if it has a full charge, you can tell how full the charge is by the blue lights. Handy.
Sorry this post is quite short, but I don't really know what else I can say. Apart from that this comes everywhere with me.
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