I needed a set of magnetic checkers for an empty Ohio Art checkers tin.
I had previously embedded magnets in a wooden Chess set but
I couldn't get the magnets to work with the wooden checkers.
I realized it would be easiest to design hollow checkers and
drop a magnet into them during a paused print.
I used 4.5 mm sphere magnets that were on hand and they proved strong enough.
The checkers will stick to the tin and also stick to each other when crowning.

I created a cylinder checker and placed a cylinder hollow inside.
I then copied and pasted together a set of eight.