The biggest rub with this is that it's less """air-tight""" than screw-down frames. This is a natural consequence of its defining feature: a magnetic closure. If this were a display case for anything else, I'd rage. It's a card holder, though, and intensely easy to crack open every once in a while to clean away the minuscule amount of detritus that'll get in, or simply switch the contents out. The card I put in it was about 20¢. I wanted it to feel special much moreso than to be completely impervious to dust. If you want to put in two cards back to back, you can, but it'll only increase the seam between the halves.
It supposedly helps with UV damage, if you're the kind of person to have windows that aren't completely covered in light-blocking curtains. And, to put your things next to them.
3 Good Enough Solutions out of 5