The inner diameter of the rings are included in the file name in millimeters. The models themselves have the US size labeled on the side. See the below guide for international conversions, it's also included in the file names.

There are two ring options for each size, one is a ring blank, the other is meant to attach to a key ring loop for easy carry(the mounting hole is 5mm diameter.) I recommend printing a ring blank of the size you are looking to buy and seeing how it feels during the day; fingers can swell and change shape quite a bit over the course of a day.

The sorting stick model can be used to check the size of rings. When you drop a ring on the sorting stick try not to push down as it can wedge the ring and be more difficult to remove. The ring should fall on the bottom line of the size it corresponds to. There is also a stand for the stick if you want to use it for ring display. The stick is 250mm tall, you can scale it on z-axis without messing with your measurements if it is too tall for your printer.
 

Printing Estimates/Stats:
(All 25-Rings wMounting Holes) = 15% Infill - 45.07g - $0.90 cost(PLA) - 2h5m printing time

(All 25-Ring Blanks) = 15% Infill - 32.47g - $0.65 cost(PLA) - 1h21m printing time

(Sorting Stick + Stand) = 15% Infill - 42.34g - $0.85 cost(PLA) - 3h22m printing time

*If you just want to print one ring it takes about 15min, cost about $0.04 per ring

Printing Suggestions/Tips:
None of the models require support material. I recommend using a brim on the rings and sorting stick. I also found using a back seam on the sorting stick looked the best.

*Note: Ring sizing can be inconsistent across sellers and the ring profile can also affect fit. Online guides can also have conflicting information, I looked at a few and tried my best to average the results for approximate accuracy. Should also consider whether your printer is calibrated properly for precise dimensions. TLDR: Don't expect perfect accuracy…

Hope this helps you pick out the right size!

----------------------------------------------------------------------------------------------------------------International Sizing Guide:

• (14.0mm) US Size 3 ~ UK F ~ Japan 4 ~ France 44 ~ Italy 4 ~ Germany 44
• (14.5mm) US Size 3.5 ~ UK G ~ Japan 5 ~ France 45.25 ~ Italy 5.5 ~ Germany 46
• (14.8mm) US Size 4 ~ UK H ~ Japan 7 ~ France 46.5 ~ Italy 7 ~ Germany 47
• (15.2mm) US Size 4.5 ~ UK I ~ Japan 8 ~ France 47.75 ~ Italy 8 ~ Germany 48
• (15.6mm) US Size 5 ~ UK J ~ Japan 9 ~ France 49 ~ Italy 9 ~ Germany 49
• (16.0mm) US Size 5.5 ~ UK K ~ Japan 10 ~ France 50.75 ~ Italy 10 ~ Germany 51
• (16.5mm) US Size 6 ~ UK L ~ Japan 12 ~ France 51.5 ~ Italy 11 ~ Germany 52
• (16.9mm) US Size 6.5 ~ UK M ~ Japan 13 ~ France 52.75 ~ Italy 12.5 ~ Germany 53
• (17.3mm) US Size 7 ~ UK N ~ Japan 14 ~ France 54 ~ Italy 14 ~ Germany 54
• (17.7mm) US Size 7.5 ~ UK O ~ Japan 15 ~ France 55.25 ~ Italy 15 ~ Germany 56
• (18.2mm) US Size 8 ~ UK P ~ Japan 16 ~ France 56.75 ~ Italy 16 ~ Germany 57
• (18.6mm) US Size 8.5 ~ UK Q ~ Japan 17 ~ France 58 ~ Italy 17.5 ~ Germany 58
• (19.0mm) US Size 9 ~ UK R ~ Japan 18 ~ France 59.25 ~ Italy 19 ~ Germany 60
• (19.4mm) US Size 9.5 ~ UK S ~ Japan 19 ~ France 60.75 ~ Italy 20 ~ Germany 61
• (19.8mm) US Size 10 ~ UK T ~ Japan 20 ~ France 61.75 ~ Italy 21.5 ~ Germany 62
• (20.2mm) US Size 10.5 ~ UK U ~ Japan 22 ~ France 62.75 ~ Italy 23 ~ Germany 64
• (20.6mm) US Size 11 ~ UK V ~ Japan 23 ~ France 64.25 ~ Italy 24 ~ Germany 65
• (21.0mm) US Size 11.5 ~ UK W ~ Japan 24 ~ France 66 ~ Italy 25 ~ Germany 66
• (21.4mm) US Size 12 ~ UK X ~ Japan 25 ~ France 67.25 ~ Italy 26.5 ~ Germany 68
• (21.8mm) US Size 12.5 ~ UK Y ~ Japan 26 ~ France 68 ~ Italy 28 ~ Germany 69
• (22.2mm) US Size 13 ~ UK Z ~ Japan 27 ~ France 69 ~ Italy 28.5 ~ Germany 70
• (22.6mm) US Size 13.5 ~ UK Z+2 ~ Japan NA ~ France 71 ~ Italy 32 ~ Germany 72
• (23.2mm) US Size 14 ~ UK Z+3 ~ Japan NA ~ France 72.5 ~ Italy 33 ~ Germany 73
• (23.6mm) US Size 14.5 ~ UK Z+4 ~ Japan NA ~ France 73.5 ~ Italy 34 ~ Germany 74
• (24.0mm) US Size 15 ~ UK Z+5 ~ Japan NA ~ France 75 ~ Italy 35 ~ Germany 75