I have a 3 month old infant that keeps kicking off his socks - even ones that go nearly to his knees.  This works to keep the socks on!  I watch his little feet move rubbing together and kicking in a way that would normally remove his socks and now they don't move!  This is perfect - especially for day care where I don't want my little one to be sock-free and freeze his toes!

Please note - I do have a 3 month old and this is the 6-12 month size.  My 3 month old was in the 50% in weight and 60% height at his last check-up.  So I suggest ordering the larger size earlier.

Also the package says to always remove these at nap and bedtime.  I do not remove them but my baby wears pajamas over his socks/sock-ons at night so they aren't IMHO a chocking hazard which is why I expect that they need to be removed.  I could see that an older infant potentially could pull them off with his hands if they were accessible (my baby is too young to have this skill).  Also the package says they aren't meant for walking or wearing with shoes.  The material is 82% nylon and 18% elastane - it is a nylon-feeling thin stretchy material - similar to the material used in thicker tights used by gymnists or dancers.