my son be 3 1\/2 month old and he sleep in he Halo Sleepsack every night . when he be a newborn we would swaddle he and then he out grow the need for it . when we use the swaddler wrap be be perfect . it be also just tight enough so he could not slip he little hand out . I also really like that it be so easy to clean !!! now he be wear a medium size sleepsack and it be perfect . I have notice that it also keep he on he back because it be hard to roll over in . that be so great because he be a little wiggly worm at night . over all this be a great product and I would recommend it to anyone with a baby !