I ordered three of these - black, grey and navy with grey stripes.  They're all the same size and they're all maternity.  I've checked multiple times because of how different they are.

I feel like Goldilocks:
The black one fits perfectly - though I wouldn't expect that to always be the case because of how different they all are.
The navy with grey stripes is too large but it's nice for comfort. It does tend to slip off too easily so you have to beware in public! Got mine caught in the wheel of a grocery cart once!
The grey one is really too tight. If I wear it a long time it tends to make me nauseous. Any pressure to my stomach makes me a bit sick right now. When I first tried it on - it was so tight I worried it wasn't even a maternity size and I was only about 4 months pregnant.

So - overall this is a hit or miss but it's super cheap compared to other maternity clothes. Even though they're not perfect, they're all staples in my wardrobe because I can't stand maternity pants and the way the CONSTANTLY slide down! I do roll the band down on all of them and think they look much nicer that way even though they're not technically meant to roll down.