Palm Power 2S 300mAh battery with a high 65C discharge rate and JST connector and balance lead for charging.  Viper compatible, great antweight (1 pound) class battery.  

 Specifications:

• Capacity: 300mAh
• Voltage: 2 Cell / 7.4V
  
• Discharge: 65C
  
• Weight: 18g
  
• Dimensions: 47.5x13x17mm
  
• Discharge plug: JST