The holder you are showing looks just like the one I got from Fisher for my
1266x. It holds four AA batteries in each holder. Mine takes two of these for
a total of 8 AA's.
They hold four. They also fit my Garrett GTA 350s and my Fisher 1266 as well as my Garrett 2500. The 1266 has a much better way of using them on the detector.
Garrett 2500, GTA 350 Tight fitting tabs cause battery cases to break.
Fisher 1266. One screw holds cover without as much pressure on
battery cases. Older is better.
The holders that Fisher sent me will not let the end cap close all
the way which really doesn't matter because I don't go near the
water with it. Other than that they still work. Yes, each holder holds
4 AA's.