I ordered the 20s in a PXS based on the size chart and they fit perfectly. Like yoga pants with
compression. Sooo as a runner (about 32 miles during the week) I do long walks on the weekends (about another 26-30 miles) I wore these for the first time on a 12 mile walk and thought I made a mistake and should have ordered the 40 for more resistance. Lol wrong, you feel it when you take the pants off!!! I was extremely surprised how tired my legs felt as compared to normal workout pants. I will eventually get the 40s when the 20s feel easy which may not be for a while. Highly recommend these pants!!