One size fits most, 5 LED lights. And works for around 24 hours in full use. Requires 2 cr2032 lithium batteries in the batteries hatch. Lick on/off built into band switch operation, operates on 2 replaceable lithium batteries. It points directional light toward what your eyes are looking at. Ideal for joggers, bikers, hikers, and even children on their way to school. Great for hunting, fishing, camping and other outdoor activities!