I bought this one - http://www.amazon.com/gp/product/B00BB5GR0A/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1

I will charge the moto x from empty to full nearly 5 times without needing to be recharged. I use it for my tablet and my moto x and it's great. Turns on when you plug something in and turns off when you remove it. Good price for the MAH.