This is the Traxxas SERIES 4 4200mAh 8.4V 7C Flat NiMH with iD Technology TRA2940X.

Features:
12AWG multi strand wire is soldered directly to the LiPo cells eliminating increased resistance from bullet connectors and accidental reversed polarity connections
iD Technology
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
Requires:
LiPo charging bag
EZ-Peak Plus 4-amp NiMH/LiPo Fast Charger with iD™ Auto Battery Identification

Traxxas 4-Tec 2.0Traxxas 4-Tec 3.0Traxxas Drag SlashTraxxas E-MaxxTraxxas E-RevoTraxxas HossTraxxas RallyTraxxas SlashTraxxas Slash 4x4Traxxas Slash 4x4 UltimateTraxxas SpartanTraxxas SummitTraxxas TRX-4Traxxas TRX-4