Lithium Polymer or LiPo battery, they have a much higher discharge rate (due to a lower internal resistance) than regular NiCad / NiMHD batteries which results in turning motors much faster (as they draw more current then normal).
By rough rule of thumb, a 7.4v LiPo turns a motor about the same as a 9.6v conventional battery; an 11.1v is more on par with a custom 12v+ battery. Not all AEGs can run such overclocked setups but G&P is a good solid brand. That said, running an AEG on an 11.1v still adheres to the laws of physics; the increased turn will result in more rapid wear of parts.
This particular Li Po battery comes with a standard Tamiya adapter. The Long G&P 11.1v batteries are very lightweight fitting into the area with a long space such as the AK or the recent Galil.
17cm x 1.5cm