I purchased 2 sets of the Nike Kids socks in a medium. The size chart online AND on the package itself states that a medium fits shoe sizes 3Y-5Y. The back of the package for both sets of socks I bought state that I bought a medium- and also includes a size chart stating that a medium fits a 3Y-5Y. Yet, the front of the same packages states that the socks fit a 5Y-7Y. And they are definitely a 5Y-7Y fit! They are too big for my 9 year old. I gave one package to my older daughter and I am just going to hang onto the other package and wait for the younger one to grow into them. I was very surprised that the sizing was contradictory between the front and back sides for the SAME package for two sets of socks.