Uses 6mm diameter by 2.7mm tall magnets. The fit of the magnets is tight, but put a tiny bit of super glue in there to make sure they don't come out. 

It is important to orient the magnets correctly when inserting them. I put all the magnest in a stack, and pushed one into the top. Then with the stack holding the orientation, I pushed each one into the bottom. This guarantees no orientation issues.

Bottom takes 8 magnets, top needs 1.

No supports needed. Printed at 0.2mm layer height, 15% infill, 3 walls/top/bottoms. 

See how nicely each position snaps in place: 

https://www.youtube.com/shorts/aaWkCkB9O1c