The First Years On The Go Booster Specification.. On-The-Go Booster Seat seems to appear and disappear like magic! Pull out the valve and it self-inflates into a sturdy and comfortable full-size booster seat; the adjustable safety belt with T-restraint helps hold your child securely. Mealtime over? Just press out the air and fold down the back. With a self-carry handle, it's compact, lightweight and ready to go. Take it anywhere! From 12-36 months.