My kid has been wearing these soon after he started walking, and he's still wearing them (in a much larger size, of course!).  We live in CA, so it's often hot, and these provide good airation.  They are sturdy and easy to clean.  My son has not managed to break any of these before he outgrew them, which is more than what could be said for several other brands we tried.  I think we will keep buying these until they run out of sizes!  :-)