Lithium battery with rheostat for use with the Spectra Iris B.I.O. and the Loupe K-LED light system. Illumination strength can be controlled by adjusting the dimmer control knob on the battery pack. The battery fully charges in two hours, and has a usable charge in five minutes. It is also lightweight: weighing only six ounce (171 grams). A belt clip is located on the back of the battery for those who prefer to carry the unit on their belt.