What are the weight and height requirements for using this booster seat?

With the back support, your child must weigh between 30-100 lbs (13.6-45 kg), be between 38-57 inches (96-145 cm) in height, have the shoulder belt positioned across their shoulders in the red zone, and have their ears below the top of the booster seat. Without the back support, your child must weigh between 40-100 lbs (18-45 kg), be between 40-57 inches (101-145 cm) in height, and have their ears below the top of the vehicle seat cushion when sitting in the booster seat.