• High-backed boosters, used as belt-positioning boosters. Most have a clip or strap to hold the shoulder belt in place. Some high-backed boosters have removable harnesses, which can be used with the harness for a child under 40 pounds.
Children who reach 40 pounds before age three may not be mature enough to stay seated properly in a belt-positioning booster. A vest that uses the belt system and a tether strap would be an option in this situation.
4. Which booster is best?
• The belt-positioning booster is the best choice if your car has combination lap/shoulder belts in the rear seat.
• Use a booster with a high back if there is no head restraint for the child.
• The booster with a high back and a removable harness provides the most options in many vehicles. Check the label for the weight limit on the harness.
5. How long should the booster be used?
• Try the vehicle belts on your child as he or she grows taller. When the child sits comfortably without slouching, use the belts without the booster, keeping the lap belt low on the hips and the shoulder belt across the shoulder. Lap belt fit is most important. A child is usually ready for the adult lap and shoulder belt when he or she can sit with his or her back against the vehicle seat back cushion with knees bent over the vehicle seat edge and feet on the floor.
• Do your child's ears come above the top of the vehicle seat back? If so, a high-back booster will improve neck protection.