Summary: If you use the MB-D12 in the field you have three power options. You can use the D4 battery (EN-EL18) with a custom cover, the D800/D7000 battery with the MS-D12EN, or AA cells with this, the MS-D12. I prefer rechargeable AAs because I can use them in my SBs, external battery pack, and laser illuminator as well as my D800 and D200 battery packs. [...]- Nikon's EN chargers aren't!
Pros: Easy To Use, Improves Product Function, Lightweight