Nikon's MB-D12 Multi Power Battery Pack for D800 and D810 Cameras is a grip that attaches to the Nikon D800 and D810 cameras. It provides extended battery power with the batteries (not included) in the grip, plus giving you a better, more secure and stable hold on the camera, making it easier to handhold at lower shutter speeds.
Customers choose the Nikon MB-D12 because it allows for faster frames per second when shooting DX. And you can get up to twice as many shots without changing a battery. Other advantages are longer use of the camera (two batteries instead of one), more convenient access to controls in vertical format photos, and faster continuous shutter releases. The MB-D12 has a tripod socket and will attach a blackrapid conector.
The battery pack is supplied with two battery trays - one that holds an EN-EL15 rechargeable battery, and one that holds 8 AA batteries. A holding case, contact cap and user's manual are also included. This power pack accepts 1.5V LR-6 (Alkaline), Lithium (FR6), Ni-MH (HR6) or Ni-Mn (ZR6) batteries.