These are very slim, extremely light weight batteries based on the new Polymer Lithium Ion chemistry. This is the highest energy density currently in production. Each cells outputs a nominal 3.7V at 1000mAh! Comes terminated with a standard 2-pin JST connector - 2mm spacing between pins. These batteries require special charging. Do not attempt to charge these with anything but a specialized LiPo charger.
Battery includes built-in protection against over voltage, over current, and minimum voltage.
Note: Be careful with the JST connectors. They can stick in pretty good and tugging on them can damage the connector. Check this tutorial for an easy way to remove them safely.