These tights were advertised as a midweight or medium weight product, but I would have to disagree. They are pretty thin-- feel like unlined spandex. They are comfortable and stretch a lot both throughout the body and in the waist band. I wear a size 6 but ordered the medium-- they'll be fine, but probably should have ordered the small. These have a pretty smooth profile and would be good for someone who needs lightweight thermal bottoms underneath their normal clothes or work uniform as I do. Definately a lot less bulk than my merino wool bottoms, but then they don't seem as warm or as wind resistant. Another good thing about these bottoms is that they don't have underwear-like crotch seaming, so you can probably get away with wearing them as a running tight and no one would look at you funny. So, for versatility, smooth/low profile styling, comfort, and affordable price, consider these thermals-- just don't expect them to be super warm!