I ordered two different sizes E&F since it was my first time. My thigh measurement is 30. Size E fit perfectly. I wore these in Cancun for about 6 hours straight under a dress. I did not even notice they were on (my dress was a little short when I sat down and these looked cute, like they were meant to show. Also even though I was sweaty, the humidity was terrible they did not move a bit. No adjusting all night. So glad to have these!