The typical plastic CD jewel case fits perfectly, but if you max out the capacity of the tray, getting one out might take a little wiggling (the solution is move one case to the next tray). They also stack securely, although we have them lined up under the bed (single stack). I found these trays to be well worth the $23 price tag.

https://www.amazon.com/Stock-Your-Home-Electronics-Organizers/dp/B0019U03N4