I normally wear a size 8-1/2 shoe and at first I thought these booties were too small for me to wear, but I managed to get in them in bare feet and after a couple of weeks' wear they stretched out enough for me to be able to wear a thin sock with them if I want to.  Now I love them!  They stay on (vs. the mule-type slippers I had been wearing), and they are snuggly warm.