After 3 c sections, I need all the help I can get.  I started with the size Large (when I was a size 12). I have moved on to the medium (I am between 8-10 now).  The medium is REALLY tight, but does the job.  I prefer the large day to day because I have 3 children under 6 to run after, and it is a bit more comfortable for that.  These things are really great.  I can't believe I didn't know about them after my first 2 c sections.  They should send all women home with them after giving birth!