I've been wearing Isotoner slippers for many MANY years, and I've never had trouble with the size until I bought this style.  I wear a perfect size 9, ordered the 8-9, and they keep slipping off my heel.  I can't imagine how large they must be for someone who wears a size 8!  Not sure if I received an extra large pair by mistake, but it has size 8-9 on the sole.  Cute style and would be comfortable if they stayed on my foot, but I rarely wear them.