The Flash Battery Pack is an external power source for a higher flash capacity. This high performance power pack is a light, compact external power source, used for Nikon flashes. The Turbo Flash Battery Pack from Aputure uses 6x 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 event photography such as weddings, and for high frame rate Canon cameras.