High-back boosters may function only as a booster seat or may have a harness for smaller children. Approved weight ranges vary from model to model, so be sure to check the instructions and labels on the seat. Shield boosters are designed to be used with a lap belt. Children under 40 pounds should use child safety seats with a harness system for best protection. Never allow a child to use a belt-positioning booster or sit in the shield booster seat without the shield while using only the lap belt.
Some manufacturers offer vehicles with built-in child safety seats and booster seats.