My feet are a nine and my daughter's are an eight.  I ordered the large size 8-9 size but the elastic was too tight and hurt my heel with each step.  Plus I almost wiped out on a wet linoleum floor.  I gave them to my daughter and they fit her much better.

The material is less soft than I hoped, but seems very warm.  I am sticking to my moccasin style slippers instead.