Titan Power 11.1V 1200mAh 25C LiPo Battery (Triple - Deans).
127mm long, 20mm wide, 6mm tall.

Titan Power LiPo:

• Superior Trigger Response
  With the best discharge rate for airsoft, this means that Lipos have a very snappy trigger with a hard to beat trigger response
  
  
• Higher Compatibility
  Made in many sizes and shapes, Lipos can not only fit in most airsoft devices, they also have a much higher chance of fitting in the less common devices.
  
  
• Safety, Maintenance, and Longevity Considerations
  Lipos can be over discharged (used to failure), have a high puncture risk (which causes fire) as the plastic construction isn’t as strong, and will generally have both less useable storage and less total life that li-ion.