I purchased the M in the high-waisted support briefs following a C-section (pre-pregnancy a size AU 10-12). The lower part of the briefs feels excellent; my scar is very well supported. However, the waistband is VERY tight and causes constriction, so I have been unable to wear them all day. When sitting, the waistband rolls down, making it very uncomfortable. They would probably work better for a smaller person who doesn't have a new collection of back rolls following pregnancy. I am hoping these will work better as my body returns to its pre-pregnancy size.