I initially purchased a small for my size 30 waist, and I held my breathe for dear life to put it on, It brought my waist in about 4 inches. By the end of the work day, I could not wait to take this thing off. I recommend wearing a tunic underneath to prevent marks in your skin from the corset. I gave it to my much thinner sister, and she loves it. I purchased the medium next, and it did not make a difference at all, and it was much longer than the small, extending under my boob, to my jeans. I returned it for a different brand, I did love the material.