Nikon MB-D10 Multi-Power Battery Grip
Description (from B&H): The Nikon MB-D10 Multi-Power Battery Grip allows the Nikon D300s, D300 & D700 to be powered by two EN-EL3e batteries (sequentially) – one in the camera body and one in the MB-D10 – effectively doubling your shooting capacity. The MB-D10 also provides a comfortable vertical grip with an additional shutter release and scroll wheel for easy access to the camera functions when shooting in the vertical orientation. It is also fairly compact, with dimensions of 5.9 x 2.9 x 1.7″ (15 x 75 x 45mm).
With the included MS-D10 AA battery holder, users can power the camera with 8 AA batteries. Or, use the Nikon EN-EL4 or EN-EL4A battery (sold separately) combined with the optional BL-3 Battery Chamber Cover and obtain a higher frame advance rate (8 Frames per second in the D300) than what the EN-EL3e battery can provide.