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 1200mAh & Dimentions 40x30x3 mm (Length x Width x Thickness)
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.