This is the Spektrum DX8 LiPo Transmitter Battery. The 4000 2S LiPo offers not only double the flight time as the stock DX8 battery but also advanced safety and features. It also includes a built in safety current that shuts down the battery, to avoid overcharging and damaging the battery and radio, as well as a built in balancing system to make sure you get the longest life and power from your pack.

Features:
Built-in cell balancer
Built in safety current prevents over charging
Specifications:
Type: LiPo
Capacity: 4000mAh
Voltage: 7.4V
Wire Gauge: 20 AWG
Configuration: 2S
Length: 70mm
Width: 52mm
Height: 20mm
Application: DX8 Transmitter Battery
Maximum Continuous Discharge: 2C
Charge Protection Circuitry: Yes

Batteries are dangerous goods that cannot be express shipped / air freighted