My son can't wear these because an area under his ankle on the inside strap rubs his skin raw.  It's not that a different size is needed, it's just what Crocs seem to do to him.  I tried this style because it didn't have the little hole punched out of the strap, which is where his first set of Crocs rubbed him, but this strap still rubs him in approximately the same place, so I guess he just can't wear Crocs.  His sister with narrower feet loves her Crocs, though.  These are super cute shoes, though, for a kid who doesn't have this problem.