This is the Dyanmite Dyna-Fun 2400mAh NiCad 6-Cell 7.2 Volt High-Capacity Flat Battery Pack.  This is a great battery pack if you want extended run-times.  It comes pre-wired with a Tamiya-style connector, and is ready for immediate use.  These are high-quality battery packs that will last better than some of the cheaper packs.