Bolt CBP-N2 Compact Battery Pack for Nikon SB-900 & SB-910 Flash Extends Portable Flash Capacity | Up to 577 Flashes Per Charge Fast Recycle Times Up to 1.92 Sec | Thermal Switch Prevents Overheating Option of Using 4 or 8 AA Batteries Alkaline, Lithium or Ni-MH Batteries In The Box: AA Battery Magazine for Bolt Compact Battery Packs, Soft Case, Mounting Screw, Limited 1-Year Manufacturer Warranty