Lightweight comfy fabric, washes well too. I received these for Christmas, and I was a little skeptical when I saw how lightweight they were, but now I love them. I tried to order a few more but they're out of stock. Hopefully they get more in next winter! I would say they run just a tiny bit small, I am 5 feet 2 inches, 135 pounds and wear a size 6, but the Medium in these PJs is perfect. I like the narrow elastic waistband, it's comfy and non binding. I like it better than a drawstring.