Hanperal 4 X 18650 Water Resistant Battery Pack Case House Cover for Bike Bicycle Lamp .Made of high quality ABS. .Supports 4x18650 batteries and combined them to bicycle lights powered. .The Output voltage 8.4V; Input voltage 8.4V;USB connector output voltage 5V. .Easy to use. Standard 5.5DC Interface(Case diameter 0.95cm, 0.5cm diameter within the interface) .Designed by One for two wire interface, can provide power for the phone and Bicycle lights( just output power).