Napkin Ring Problem

I watched this video the other day:
https://youtu.be/i8GD33DsRw8

And this one today:
https://youtu.be/J51ncHP_BrY

So I decided to make some 3D printable napkin rings. They all have the same volume.

There are three rings, all 40 mm in height. Shpear radii are 25 mm, 50 mm and 75 mm.

Assembly is all three in one STL.