#3. "RE: SD-9 battery pack and SB-800" In response to Reply # 0
If you look at the SB-900 manual, you will see there is a cut out for a key tab on the SB-900 socket not present on the AB-800's socket. This key tab is on the SD-9 plug but not on the SD-8 plug. The SD-8 will fit the SB-800/900 and the SD-9 plug will only fit the SB-900.