My tall 5 month old son fits in this costumer perfectly! I love it and it's worth the price! =)I don't know if he would still fit into it at nine months but it is pretty stretchy and light enought that I can have him in a onesie underneath for cooler October weather. The only thing that doesn't work for us is the head cover, but we had planned to use a Naruto Jiraiya headband instead from the beginning.