A 11.1v Lithium Polymer (LiPO) is functionally equivalent to a NiCad / NiMHDd battery in the custom 12-14v range yet achieves this performance with much lower weight and size. With a small Tamiya type connector, this little tike is good for driving low powered AEGs at high cyclical rates of fire.
At 1cm x 2cm x 9cm it is such a tiny little thing that it affords you a lot more carry solution options than larger battery types; even by LiPo standards it is small. With an 1100mAh capacity thats a lot for its size but as the battery is tiny it is easy to carry a spare or two with minimal impact on carry inconvenience.
Be sure to use a balanced charger when charging LiPos, BOL makes their own multi-charger which is a good choice. BOL also makes an 7.4v LiPo that is even a little bit smaller still.
9cm x 2cm