The Nikon MS-D12 AA Battery Holder for MB-D12 Multi-Power Battery Pack allows users of the Nikon D800 digital camera with the MB-D12 Multi-Power Battery Pack to use 8 AA batteries instead of the Nikon EN-EL15 lithium-ion battery. This is especially useful when shooting in cold weather. Also, you can keep an additional MS-D12 AA battery holder pre-loaded, so that you can quickly swap out battery sets.
For MB-D12 battery pack for D800 camera