The BG-E6 is dedicated strictly to the new EOS 5D Mark II, and permits one (or two) LP-E6 battery packs to be installed. With two packs, the already-impressive battery life is doubled, compared to using a single LP-E6 pack in-camera. Especially for extended use of the EOS 5D Mark II's movie mode or Live View, the BG-E6 is an outstanding accessory.
Like previous Canon battery grips, the BG-E6 provides full vertical shooting controls, which can be independently turned on or off as the photographer desires. Many users find the battery grip can enhance camera handling, especially for shooting vertical pictures.
Please be aware that the battery grip BG-E4 for the previous EOS 5D is not compatible with the new EOS 5D Mark II camera.