First of all, they fit fully into single-row card boxes so I can use them for any size box. They also have write-on index tab that fold over to make the divider more visible in boxes. They also won't bend, fold, fall over, etc without some serious effort. They are not made out of cardboard or whimsy plastic, it's a 30 point polyethylene plastic that would take some effort to fix.
I haven't fully put these in place yet in my card boxes, because I wanted to give them a practice go first and decide which boxes I wanted them in first. But, here is an example of my practice run:
The tabs fold back once you are ready for them to. I wasn't ready to do mine yet as I haven't written on them and I think it will be easier to write on them being flat.
If you have the same problems as I did with keeping cards separated in boxes and not knowing what to use to divide them, I suggest giving these a go. They seem to be a very solid product. You can find them on the BCW Supplies website, HERE.
Let me know your thoughts on these below and if you have the same issues I did.