I used the size 3 for my 10 month baby, he developed severe rashes after just a few days of use. I have been using swaddlers since his birth, never had any issue. We switched to this because of the ease of putting it on and taking it off. Just after a few days of using this, my baby started becoming very fussy at the time of diaper change. Then he was very itchy near his genitals. We went to the dr. who diagnosed it as a severe rash. I wouldn’t recommend this to another parent ever.