JJC For Nikon Camera- Battery Pack The JJC FB-2(II) Compact Battery Pack is used to greatly increase the number of flash firings of the NIKON SB-900 Speedlight, and also shortens the recycling time.
Total minimum flash recycling time can be as fast as 1.5 seconds when used with AA Ni-MH batteries, and the capacity per round of batteries is about doubled.
Batteries must be in place in the flash in order to operate.
