The high back booster seat does not have its own harness or belts. High back child booster seats incorporate a system for positioning the existing car seatbelts correctly for the safety of the child. They have a built up back and side that offer additional comfort, support and protection for the child. It is the correct fit and positioning of the seatbelts provided by the car booster seat that greatly reduces the risk of serious injury to the child during an accident and ensure that they do not slip out of the belt or sustain the force of the impact in a way that can increase the chance of injury. If your vehicle does not have headrests then a high back booster is required to provide the protection and head restraint that can reduce the risk of whiplash in certain circumstances. Also the high back designs that incorporate the shoulder belt guides help to stop the belt moving up to around the childs neck area or the child slipping the belt under their arm or around their back. All of these examples can be very dangerous and result in serious injury in the event of an accident. As children grow at such a pace they can soon outgrow the high back car booster seat. Many designs are adjustable in height to account for this growth or have removable backs for conversion into a low back booster seat design.