The Flash Battery Pack is an external power source for a higher flash capacity. This high performance power pack is a light and compact external power source, used for Canon flashes. The Turbo Flash Battery Pack from Aputure uses 6 AA batteries (not included) and connects to most Canon flash units. The Turbo Flash Battery Pack also attaches to the bottom of the camera for easy portability via an included camera screw, that stores in the battery pack when not in use. This is a must for high-frame rate Nikon cameras and for event photography such as weddings.