This is the Associated Reedy Wolfpack NiMH 7.2V 4200mAh Stick Battery Pack with Tamiya (Standard) Connector.
FEATURES: Sport pack for cars, trucks, boats and other items that require a stick pack
Nickel Metal Hydride (NiMH) alternative to NiCd packs
INCLUDES: Wolfpack NiMH 7.2V 4200mAh Stick Battery Pack with Traxxas Connector
REQUIRES: NiMH capable charger
SPECS:

Capacity: 4200mAh
Number of Cells in Series: 6
Rated Voltage: 7.2V
Minimum Discharge Voltage: 5.4V
Discharge Lead: 14AWG 4" (100mm) long wire with Tamiya connector
Pack Dimensions: 5.3" x 1.75" x 0.875" (135mm x 44mm x 22mm)
Cell size: Sub-C