I purchased two of these belly bands (black and white with lace) as well as a one-size-fits all from motherhood for about $15.  I find very little difference in quality and utility, so you might consider your alternatives- these are pretty expensive for what you get.

That said, having a belly band has really saved the day for me, and I highly recommend them to all pregnant ladies out there.

A note on sizing, I was between sizes (2 and 3 I think) and opted for the smaller one.  I'm glad I did, it fits quite well, at least for me at 23 weeks. By the end, I'm guessing I won't be wearing my nonmaternity pants so no biggie if I grow out of it. It's similar in fit and size to my other one-size band, a curious thing....

As a friend of mine also pointed out, these make nice tube tops to sleep in for light support up north....