It is called Key Chain
Key Ring, actually.
There are several: HandyCards, CardStar, etc. Key Ring is the one I was using, but I found that no one here would accept it. None of the grocery stores or anywhere would scan it.
So it was useless for me.
Duh, reading his post while typing, Yes Key ring.
I only have it because my wife has so many of them damn cards so I thought I may as well copy them for when I am in stores alone.
The scan isn't an issue, they just plug the number in, I have invisible shield on mine and not once have I crossed a problem.