Standard sized Joye eGo battery rated at 650mAh, with a threaded cap at the end.  With the cap attached, it looks and performs just like the 650mAh eGo battery.  It can be charged on any of the Joye eGo fast chargers.

 

Here's the cool part.  Unscrew the endcap and put it in your pocket.  Hidden underneath is a standard USB mini charging port.  Attach the included USB cable to your computer or USB adapter, the other end to your battery.  This will charge your battery and allow you to use the device as a passthrough.  Very cool design on this one, the overall length is just a bit more than the standard eGo battery.

 

Compatible with all 510 and eGo series atomizers