The Phottix Premium Series BP-5Dlll Vertical Grip/Battery Holder WAS DESIGNED for the Canon 5D Mark lll digital cameras. This battery grip can hold two camera battery packs or 6 AA batteries. It is equipped with a vertical-grip shutter release button Main Dial, Airlock/FE lock and AF point selection controls for easy vertical shooting. It works with 1 or 2 rechargeable camera batteries. The grip also has a built tripod socket