Bought these as a gift for my daughter, she reports that the size is perfect (and she says they run a little larger than expected, so if you're not sure between two sizes, probably go with the smaller) and they're exactly what she wanted.
I'm 110lbs and have some curves and a little booty. I had previously ordered the Medium and it fit me slightly loose/comfortable fit. This time I ordered the red in Small and it fits like a glove. Haven't washed it yet but from what i read from the previous reviews i will either hand wash it or wash it in a cold cycle to avoid the red color staining the white band.
I'm a 6 in most underwear, including Hanes and Fruit of the Loom. I got a medium and they fit perfectly! They are so soft and comfortable. All seams and edges super smooth. I love the thick waistband. Very flattering, too.
They do scoot up your bum a bit, but I don't find it bothersome. The fabric is good with sweat, although the waistband can get a bit sticky, but still dries off quick if you give it a bit of air. The stitching is so soft.. I hope it doesn't get damaged in the wash! Maybe I'll make an effort to not wash it with any zippers or velcro.