So these are weird. When I saw and ordered these, I though that they would be meshy and smooth like my other tech underwear. But at first glance, they look and feel like woven cotton. They are actually a polyester blend though. Then they have solar dri fabric that absorbs infrared rays and converts them to heat. I’m no scientist but is that how infrared works. Eep. if you are wearing pants. But I have to admit that they are warm, like my long johns. So maybe there is something to the science.