The Frontier ClickTight Harness-2-Booster Seat can be used in Harness Mode for children 2 years old and 25 lbs up to 90 lbs or in Booster Mode for children 40 lbs up to 120 lbs. When your child is ready for Booster Mode, the harness can be safely tucked away the within the seat to easily transition the Frontier ClickTight into a high-back Booster without any hassles. Whether you are heading to the market or hitting the open road, you can travel with the peace of mind that your growing child is comfy, safe, and secure now, and for the adventures yet to come.