The crochet open-back maxi cover-up pairs a crew neck and long sleeves with an extra-open back. Its crochet structure and back cutout make coverage depend on the layer beneath, not just on a size label. Plan the exact underlayer and hem before deciding whether this is the shape you want.

Make a coverage map

Try the swimsuit, slip or other layer you would actually wear beneath a similar open-knit garment. Mark where your underlayer ends at the front, sides and back. Ask for a front and rear image of the chosen White or Red option over a contrasting layer, with a ruler showing the lowest point of the open back and the approximate size of the crochet openings. The listing calls the back extra open but does not provide a depth or opacity measure. Do not assume the knit becomes opaque when stretched or wet.

Compare the overlapping intervals

S lists bust 28.35–33.07 in, sleeve 24.02 and body length 51.18. M gives 29.92–34.65, 24.41 and 51.57; L gives 31.5–36.22, 24.8 and 51.97. The bust bands overlap, while sleeve and body length change less than an inch across the range. Ask whether bust is a relaxed-to-stretched garment interval or body guidance, then compare a cover-up you own over the same underlayer. A bust number by itself cannot establish back coverage.

Mark the maxi hem

Use a measuring tape on the reference garment to place 51.18 and 51.97 in from its stated length origin. Check the hem while standing and walking with your intended shoes. The source names a cotton blend but gives no percentages, stretch recovery or wet-use test, so ask before relying on those properties for a beach outfit.