I own three pairs of Acorn slippers, love them all. There is something wrong with the design of these.  I ordered them as I felt that the double Velcro closures would keep them secure on your foot, they don't.  Your foot slides from front to back of the mule, and it seems that you could really hurt yourself in these slippers.  I've tried them with thick wool sock, thin cotton socks, no socks, and unfortunately the results are all the same.  To look at they seem like they would be the perfect solution to tired feet, but the chance for a serious injury is there.  I would not recommend these to anyone!!!!