The SK-6 allows you to use the SB-28, SB-27, SB-26, SB-25, SB-24 and SB-22 as a grip-type flash. It also offers remote-flash capability. Used as an external power source in combination with the speedlight's own power source, the SK-6 reduces minimum recycling time by about half and doubles the total number of flashes available. It accepts six 1.5V LR6 (AA-type alkaline), 1.2V KR-AA (AA-type NiCd) or 1.5V FR6 (AA-type lithium) batteries. The SK-6 can also be used with the Nikon DC Units SD-7 or SD-8A.