If anybody was wondering about these, I bought one as a curiosity. Verdict: Okay enough for regular size cartridges and manuals, not so great for overlays or Imagic games/manuals. I can at least display the game now, but I still have to store the inserts separately.
The overlays fit if you bend them a little, but if you're bending your overlays you probably don't care about buying boxes for things. Imagic carts are too long to fit in the holder, and the manuals are larger than the inside of the case. There is no clip for smaller manuals, so they just sit loose inside. There's a piece of adhesive foam you can peel out and move around to snug your game into place, if it's not an odd size. The color's also weird, and the text is just a little blurred. The last picture is just so you can see that regular carts/manuals fit.