This is the Traxxas SERIES 5 5000mAh 8.4V 7C Flat NiMH with iD Technology.

Features:
12AWG multi strand wire is soldered directly to the LiPo cells eliminating increased resistance from bullet connectors and accidental reversed polarity connections
Semi rigid construction does not require a hard case and eliminates wire harness connectors that can loosen and fail
iD Technology
Engineered specifically to fit Traxxas models
Requires:
EZ-Peak Plus 4-amp NiMH/LiPo Fast Charger with iD™ Auto Battery Identification
Specs:
Length: 160mm (6.3")
Width: 49mm (1.9")
Height: 25mm (0.98")
Charge Rate: 3A