I wore this band for about 8 weeks after I gave birth.  It is very uncomfortable and it rides up when I am sitting down.  So unless you are planning to be sitting most of the time after you gave birth, this product will ride up to your waist.  Also, it is bulky so it did not fit underneath my clothes.
I am 5'2" 114 pounds and a size XS/S, 25-26 inch waist and 36 inch butt area BEFORE pregnancy.  I only gained 25 pounds from my pregnancy and about 2 dress sizes.  And this belt was BIG on me after I gave birth.  I got a size XS/S for this belt.
This belt was very comfortable to wear all of the time or underneath my clothes when I go out so it was hard to try wearing this all of the time.  I tried wearing it when sleeping, so that it fits right where it should and not be touches or moved.  But it was very uncomfortable so I was not able to fall asleep with this belt worn on.
And after wearing this belt for about 8 weeks, I still could not fit back into my old pair of jeans (before pregnancy).  I measured myself and I have not made an progress with this belt.  It has not worked for me.