I initially purchased the smaller socks when my little boy was only 5 months old and to be honest they did not stay on his feet however after absolutely hating all other socks I purchased recently I decided to give these another go and they are by far the best socks. My only suggestion would be to be able to buy packs of darker ones all together in a multi pack as I now have lots of white ones and only a few darker ones. They stay on and he doesn't slip in them as they have the little rubber-y bits on the bottom of them and they don't leave uncomfortable dents round his ankles.