I am a US size 16 and I ordered the 6XL size and they fit great. If you've tried Thinx's air style panties these are very like those -- breathable, almost sheer fabric overall, with a layer of absorbent material where it counts. I've knocked off one star for the description being a little off: they are not seamless.
I've tested these now, if you know what I mean, and they work! I think there's a PUL layer in there somewhere because they absolutely don't soak through! I'm really pleased with these.
Just got to use these, excellent quality! Does what is intended!