Once children reach the highest weight or height allowed by a forward-facing car safety seat, you can transition to a belt-positioning booster seat. A booster seat should be used until the vehicle lap-and-shoulder seat belt fits properly without the assistance of a booster seat, which typically happens when children reach 4'9" in height and are between 8 and 12 years old. Until a child passes the Five-Step Test, a booster seat is needed to keep your child and their seat belt in the correct position.
The two standard types of booster seats available are the high-back and the backless. High-back boosters should be used in vehicles without headrests or with low seat backs, and backless boosters can be used safely in vehicles with headrests and high seat backs. While high-back booster seats are the more secure of the two, backless booster seats tend to be smaller and lighter, making them easier to travel with.