This product includes the following:(pictures are of actual items included):

Nikon MS-D12EN Battery Holder (1):  The MS-D12 is a battery holder for the MB-D12 Multi Power Battery Pack and is used when you want to power the D810/D800/800E using the Nikon EN-EL15 Rechargeable Li-ion battery.

Nikon MS-D12 AA Battery Holder (1):  The MS-D12 is a battery holder for the MB-D12 Multi Power Battery Pack and is used when you want to power the D810/D800/800E using AA batteries.

Nikon Holding Case for Battery Holder (1)

Nikon MB-D12 Multi Power Battery Pack (1):   The Nikon MB-D12 Multi Power Battery Pack is a vertical grip for select Nikon cameras including the D800, D800e, and D810. The MB-D12 allows use of several additional power sources for extended run times without interruptions to shooting. The MB-D12 features an extra set of the main camera controls that allows shooting vertical images from a more stable stance and it counterbalances larger lenses.

The MB-D12 is compatible with the Nikon D800, Nikon D800e, Nikon D810, and Nikon D810A camera bodies. The grip can use three different battery holders for a range of extended power options. Using the MS-D12EN Li-ion Rechargeable Battery Holder [INCLUDED] adds power from one EN-EL15 battery [not included]. The MS-D12EN also features a door for a power cable so EN-EL15 shaped AC Adapters can be used instead. Using the MS-D12 AA Battery Holder [INCLUDED] adds power from eight AA size batteries. The ubiquitous nature of AA batteries and vast range of charging options such as solar chargers makes this capability most valued when shooting in the wild. 

The MB-D12 has a set of controls oriented for vertical shooting. The grip features it's own: shutter release button (with button on/off switch), 'AF On' button, front control dial, rear control dial, and multi-select stick. The control orientation allows the photographer to take vertical images with their right arm and hand in a more natural comfortable position (not overhand or underhand).

The extra mass of the MB-12 helps resist vibration while also shifting the camera & lens combination center of balance closer to the photographer thus making it easier to hold still. Photographers with larger hands will find the additional grip area a welcome improvement to camera body ergonomics.

The MB-D12 is easy to add or remove quickly. All you have to do is remove the connection port cover on the bottom of the camera and screw the grip into the camera's tripod socket. The grip also has built-in storage space for the camera port cover to keep it from getting lost.

If you ever use a longer lens handheld the MB-D12 is an especially handy accessory for your D800 or D810.