Yes. I put my Wonderswan Color in one and closed it. There is a very slight battery caused bulge, to the point of if I wasn't looking for a bulge, I would not see it. (sorry no photo to prove it). You would be wise to make some kind of insert for the UCG to prevent movement. I do not keep any of my systems in UCGs. I found a GameStop branded DS case a few years ago that all my hand held systems fit in, so got seven of them and use them a separators for the games on my shelves.
