I got this when my baby boy was maybe 3 weeks old and 7 pounds or less- the smallest glasses strap didn't didn't fit him but I got them when I did since knew I wanted these for when he was older (and they make a really cute photo prop). I like how these glasses come with two straps and a nice hardshell case. Even if your baby is too small to wear these now, they eventually will grow into them, so just get them!