The Nikon MB-D14 Multi Battery Power Pack gives you a firm, steady grip on the D600 that you'll appreciate with longer lenses or low shutter speeds. The grip also gives you greater control when in the vertical or portrait position. Instead of grappling for control on the camera body, the grip provides an easily accessed vertical shutter release button, AAE/AF lock and dual command dials.
And when it comes to power the MB-D14 is a real omnivore. Nikon has provided you with a MS-D14 AA Holder allowing you to use Ni-MH, Alkaline or Lithium AAs, as well as a MS-D14EN Battery Holder for use with EN-EL15 battery. 6 AA Alkaline batteries will give you about 450 shots while the optional EN-EL15 battery will give you an impressive 1,800 shots. That's a long time before recharging.