
Just a DVD case that has 27-28mm wide spine, usually for holding 6-8 DVDs.
Just remove flaps from inside and it holds NES, SNES, N64 & many/all other cartridge games nicely but loosely.
for more secure hold use foam (I don't)
UGC sized covers fit nicely. for perfect fit you have to strech image 5mm, but even without streching the covers look really good.
Here is pictures of my collection (part of it) showing these cases in use:
http://www.thecoverproject.net/forums/index.php?topic=2738.0