These pajamas are supposed to be flannel material. They are 100% polyester according to the tag and a twill contrast flannel according to the website. The fabric to me feels almost like lenin, very thin. Not warm and cozy as I would expect. They have pajama day at school but I can't send my son in these thin see through pajamas. It's cold here in Kentucky. I am just really disappointed in the fabric especially for the price. My son is a hot sleeper though, so he may want to keep them.