I usually avoid clothing that says 'one size', since anything made in China, India, etc. is usually much smaller than U.S. sizes.  I was actually pleasantly surprised that it fit fairly well, even though I'm not exactly svelt. I'm 5'7', short waisted, long legs and about 170 and (after a pressing), this fit pretty well. I would have like it to be a bit looser, but all in all, I like it and it's quite cute.