This is the V-MAXX Super Duty 2400mAh NiMH Battery Pack Set designed for the Traxxas E-Maxx but can be used in any electric vehicle.  This includes two batteries.  If you want excellent performance, batteries are a good way to get it.

Features: 6 sub-C cells, 2400mAh, NiMH, Stick pack, standard Tamiya battery connector.

Includes: Two packs

Specifications:
Length:   5-1/4"
Width:    1-3/4"
Height:   7/8"