Not very adjustable
I purchased one of these for my kid. We tried to use the added foam pads so it would fit better but they refused to stay seated and repeatedly pushed up toward the top of the helmet. We returned it and purchased an adult small that is adjustable in the back, which fits him much better (he is 9). My advice would be to spend the extra $40 so your child has a helmet that actually fits properly. Or spend an extra $70 and get an adult small with vents that open/close. My only complaint with the Giro helmets as a whole is that the lining is not hypoallergenic so one of my children has to endure massive head-itch while skiing.