The Nikon SD-8A is an external battery pack for select Nikon Speedlights which can provide faster recycling time and longer battery life. It takes 6 AA batteries in addition to the in-flash batteries, and connects to the auxiliary power connector and PC sync terminal on your flash. This device is compatible with SB-11, SB-22, SB-25, SB-26, SB-27, SB-28, SB-28DX, SB-80DX, SB-800, and SB-5000 Speedlights. Includes beltpack; batteries and flash are sold separately.