This is the Traxxas Power Cell 11.1V 4000mAh 25C 3S LiPo Battery.

Features:
Semi rigid construction does not require a hard case and eliminates wire harness connectors that can loosen and fail.
Engineered specifically to fit Traxxas models.
New high current connector with gold-plated copper terminals and integrated balance connector.
iD Auto Battery Identification allows Traxxas iD equipped chargers to automatically set and optimize charge settings for specific battery.
MAXX cable high-efficiency 12 gauge silicone jacketed wire.

Includes:

(1) Battery with High Current Connector and Integrated Balance Plug

Requires:
LiPo compatible charger such as the Traxxas EZ-Peak Plus
LiPo charging bag

Specs:
Configuration: 3S1P
Continuous Discharge: 25C (100A)
Max Burst Rate: 50C (200A)
Watt Hours: 44.40
Charge Rate: 1C (4A)
Dimensions: 5.3 x 1.02 x 1.7" (135 x 26 x 43mm)
Weight: 11.1oz (316g)