If I recall it right the SD-8 is for the SB24/25/26 The SD-8a for the SB28 and SB600(?) and SB800 I use the 8a with a SB800 and it's very nice. Ralph
Nikon changed the shape of the power connector to comply with EU safety regulations. The "a" model is not backwards compatible with older flash units, and vice versa. Concurrrently they restricted sales of the older battery pack SD-7 to the non-European market (SD-7 and SD-8 could be used interchangeably).
