The 10. Since these are for kids I expected better durability and am disappointed. I wont go through all of my efforts to overcome its effects. Good job Quiksilver! USB C is so much better and faster in every single way. Much more compact storage than hanging perpendicular to the wall by a wheel. Not changing to 4 stars yet, because I really love these slippers. Overall these are good. Love the color tho. I ordered my usual size, 10M.