The Streamlight Ni-MH battery stick, the chemistry is Ni-MH, that is, nickel-metal-hydride, and it's meant to be a replacement for other Ni-MH batteries. Streamlight is a well-respected American company that manufactures the toughest and most capable flashlights out there. A battery stick is similar to a battery pack, in that it is actually multiple batteries bundled together. The voltage on this battery stick is 3.6V, more than double the voltage of a typical alkaline primary cell. This battery stick is sub-C in terms of size. The Streamlight battery stick is certainly going to become an essential part of your Streamlight supplies.