I got this because I don’t have $25 for a ring specific mandrel, however I couldn’t find too many specifics about the diameters. Only the top and bottom sizes are listed on the package. Here are my measurements, the numbers in parentices are the listed sizes.

Finding ‘official’ ring sizes has been somewhat difficult, it seems that they vary slightly so these are just ones that I chose to use. I took my measurements with some thread and a tape measurer, they’re not perfect but hopefuly this can give you a general idea of what size each level is.

I assigned each level a letter for ease of reference, “A” is the smallest topmost level and “L” is the bottom.