Interesting, I have been looking for something like that.
Do you happen to know if they work well with rechargeable AA batteries, such as Energizer NiMH? I seem to recall that in some instances the rechargables may be a hair thicker than their standard counterparts. I am concerned that this may pose an issue when dealing with a very tight fitting case.
I keep DuraCell Recharges in them without issue, and those are a HAIR thicker which means you need to squeeze those bastards in. Not as easy in, not as easy out.
I don't use Recharges as much as I would like, I try to as much as possible but at times you don't have access to recharge the spent bats especially for a extentend period of time. So 90% of the time I have standard AAs in them, I just wish they made a "fat pack" with two of those back to back (like a 8 pack) as it would be very handy for me...But then again theres nothing some glue, and tape can't fix or make.
But ultimatly I cannot say enough good things about those, very high praise for a battery holder I know, but it does its job and it does it well. I keep a pair of 123 and AA holders in the orange in my pack and they are easy to find at any time, it keeps them together so theres no digging for a loose one. I've even gone so far as to rig up a little mesh pocket for them in my pack, keeps them right there and quick to grab.
The other colours are...well its a different colour, still does its job and does it well. I keep two others (AA,123) in my gear in a pouch and love them. If you've ever had to do a high stress battery change you don't want to be fumbling around with them. You want to be able to one hand the holder, pull two out and slap them in and go. With these holders I can do just that, a one hand no look bat change which at times comes in very handy and in a pinch when you don't have time to stick them back into a pouch its quite easy to just palm or pocket the holder.
The 4x holding ability works out quite well as its nice to know that you have a spare set incase something occurs, I've had friends who needed a set right after I did a change out on my light and if I had been carrying only 2x they would have been screwed...Of course I always carry enough batteries to power a small city

so its never a issue. But its just nice to know you've got that backup backup set.