I was skeptical & scared to order the wrong size, i'm 5''8 126 lbs, i typicall wear a size 2 in women & 3 in juniors & if stretches i'll squeeze into size 0 & 1 and I am too vain to buy size medium but i ordered a MEDIUM since all the other reviews said to size up.  Looking at the product it was a tiny little thing like for an infant haha but it fit perfectly.  It really lifts up the backside,perhaphs TOO much for me since i have most of my weight on my backside lol that makes me look almost fake but definitely can't wait to wear it with a sexy fitted dress & see what the bf thinks.