Feamos 4 x 18650 Water Resistant Battery Pack Case Cover for Bicycle Lamp Can be packed into 4x18650 batteries and combined them to bicycle lights powered Output voltage: 8.4V, Input voltage: 8.4V Standard 5.5DC Interface (Case diameter 0.95cm, 0.5cm diameter within the interface) Cable: 60cm;(it have the USB cable ) Can put 4x18650 batteries in to power bicycle lights (Batteries not included)