I have this sleep sack in small and medium and I plan on buy it in the large , if my little one be not stand up by then . we daughter like to kick she blanket off in the night and then would wake up because she be cold . we get the small sleep sack and she would sleep soundly through the night . she be 6 month old now , and 18 lb . and the medium sleepsack have be equally wonderful . I do not have to worry that she be get cold now , and she actually like to be zip up in it ! I also do not have to worry about blanket come untucked and be pull over she face . to wash , I just throw it in the washer and then the dryer and it come out beautifully . I highly recommend this item !