I received these as a bridesmaid gift (best idea ever) and they are the warmest, comfiest slips I've owned. I wear a size 9, and found them to run true to size with no or very thin socks.  I just bought three more pairs for my work girls, and they were a hit.  For The girls that wore 71/2, I got them 8s and they were fine.  For the teeny tiny size 51/2 in my office, the 6 was fine for her.