Read diameter and fit labels
Find the dimension that describes the actual opening.
Separate inside and outside dimensions
The overall width includes the band. The relaxed inner diameter is measured across the opening before stretching. A strap’s total length is different again. Use the manufacturer’s sizing chart for the intended fit.
Treat snap positions as separate sizes
Three snaps tell you how many positions are available, but not the size at each one. Ask for the inside diameter by setting. For a flexible ring, ask for the relaxed opening and the maker’s fit guidance.
Do not infer fit from a stretch claim
A listing may say stretchy without specifying how the material behaves or how easily it releases. If there is no size or removal information, choose a clearer listing. Never force a ring on or continue wearing one that causes discomfort.