This blue patchwork mini dress has a low back, thin straps and an S–XL chart. A useful first check is whether the bust and waist of one size both work for you; changing the strap position will not fix a waistband that is too tight.

Compare two circumferences

The listing gives S as 70 cm bust and 60 cm waist, M 74 and 64, L 80 and 68, and XL 84 and 72. For example, a shopper comparing a garment with a 76 cm finished bust and 66 cm finished waist cannot simply take the smaller of the two letters: neither M’s 74/64 nor L’s 80/68 has been identified as a recommended body size. Ask whether the listed numbers are relaxed garment measurements, stretch limits or body guidance. Then compare the chosen size with a similar dress laid flat and doubled at each point.

Length rises 68 to 71 cm across S–XL, but the source does not give the measuring start point or the depth of the back opening. Request a back view and a top-edge-to-hem measurement for the selected size before planning an underlayer. The page says 95% polyester and 5% spandex and calls the fabric stretchy; no stretch test or lining map is provided. The patchwork is a design fact, not evidence that every panel has the same opacity or give.