I bought these in medium based off the size chart and I am typically between a medium and small in running tights. When I put them on I was skeptical because they were less tight than my typical running tights. BUT these were perfect on the run--didn't have to stop and adjust them once. Also they are nice and long. At 5'7" tights tend run a half inch to inch short on me, but are too long if they are available in a long, these were just right.
They kind of have a Goretex feel to them and make a little "swishy" sound when walking. Stopped noticing it when running. Great at keeping out the cold wind. No chaffing. Soft inside. I got a size S. I am 5'6" and 120 lbs. A little long so a great tight if you are taller.
These pants are excellent for running, cycling and walking. I've used it on both winter running and cycling and it's added warmth and safety to me.