I have had the hardest time trying to transition my 9 month old daughter from her rock n play to her crib as well as napping in her crib verses her swing. She is a scream crier that has a hard time calming herself. Well this sleep sack has cured that big time. She cried a total of 4 minutes verses hours before calming herself down last night and has yet to cry today. It is such a night and day change! Thank you, Halo!