I'm size 22, I ordered 6XL after reading the reviews about the sizes mismatch, and it fits just right.
I'm not 100% sure which size I got because I ordered 6XL, and the outer package said 6XL but the label on the actual cover up said 5XL.

I like it, and I plan to order more in different colors.

The only thing that I would like to see better is the straps. They seem too thin and fragile.