My baby has worn these since she was born.  She's now 5 months old and will continue to wear them for at least a few more months. They stay on her feet better than any other socks I've tried, but she can kick them off over the course of a long car ride when DH's working at it.  I couldn't ask for more from a baby sock though.  I'm very happy with these and would recommend them to all my friends with young babies.