The number in a title, such as 8mm or 10mm, is the bead. It is not your wrist.
Stretch strands are one length unless the product offers a size. Wrap a strip of paper where a watch would sit, snug but not tight, mark the overlap, and read the centimetres. If the strand feels tight, do not force it on.
Adjustable pieces, including the Rhône bracelet, use an extender chain. Sit a charm just inside the wrist bone. The chain sets the length. There is no separate S, M, or L.
Custom or resized pieces are not covered by the 30-day return.