I'm returning mine right away. You're not missing something- there is no reference to a shoe size associated with the S/M/L/XL/XXL order options for these slippers. Trying to order the right size proved a nightmare, hope is all I could do that the XL would be appropriate for a size 13. However, when my order arrived, included in the box was a wonderful little size chart that would have been oh-so-handy at the time of ordering. Why this information is made available AFTER the fact I can't imagine, but it's a nice confirmation that yes, I must be an idiot at slipper ordering and yes, those XL's look too small for a reason. They are!So for those of you yet to order, perhaps this tid bit of information will help you make a more educated decision, courtesy of my box containing slippers of a useless size that are goin' back: S= Men's NA, Women's 5, M= Men's 5.5, Women's 6, L= Men's 6.5, Women's 7.5, XL = Men's 8, Women's 9, XXL= Men's 9.5, Women's 10.5, XXXL is Men's 11, Women's 12. So a size 13 must be unheard of in the land wherever these are made. Good luck!