The Nikon SD-8A Battery Pack takes six "AA" alkaline, lithium or NiCad batteries. It can be used with the SB-11, SB-22, SB-25, SB-26, SB-27, SB-28, SB-28DX, SB-80DX, & SB-800 Speedlights, as well as the SK-6A Power Bracket. Total flash capacity per round of batteries is doubled, and flash recycling time will be cut by 60-75%. Batteries must be in place in the flash in order to operate.