The Cosco Pronto Belt-Positioning Booster Car Seat works for children ages 5 and up. They have to be x amount of pounds and x inches tall, and the strap has to go across their chest, not their neck, but this car seat is for the 5 to 9 year old in your life. This one was used by my second child. She loves the cup holders on each side, and now that she is old enough to go without the back on it, she loves the way she feels taller, without the trapped feeling the belt sometimes gave her when it was locked over her shoulder. She absolutely loves the big kid feeling that her Cosco Pronto Belt-Positioning Booster Car Seat gives her. And I love the fact that it keeps her safe and in her seat. Of all the times I have had to stop suddenly, or even slowly, she not once flings forward because this carseat allows for the belt to be adjusted properly over her, to keep her in place. And even when it is just a backless booster as the last stage of this becomes, it still is designed to keep them in their seats with the lap belt stuck through it as it is supposed to be. It raises them up just high enough that the lap belt portion of the Cosco Pronto Belt-Positioning Booster Car Seat can fit snugly at their waist like it is supposed to, to keep them safe and sound. And best of all, once they reach 4ft 9 in, they can sit in just the Booster piece without the need for the backing, and this car seat allows it to come apart like that, so they can have just the booster at that point. It is so easy to install. All you need to do is pass the seat belt strap through the loop and then pull it down over their shoulder, and make sure the lap belt is on their lap. And the booster portion is great for plane rides, too as they just need to carry it with them and sit on it, strapped in. But the backing part isn't too good for planes as there is no shoulder strap to hold them in with. It's so simple to switch between cars, too. Just take the strap out of the loop and remove the car seat and put it in a new one.