Designed for the long haul, this versatile car seat converts from a high-back booster to a no-back booster, providing years of comfort and safety from preschool to preteen. The Nuna AACE takes security seriously, featuring a side-impact protection system made with energy-absorbing foam and a metal frame for superior protection. It features a one-hand, 9-position, height-adjustable headrest that works simultaneously with the shoulder system, which expands out as your kiddo grows. The seat also features 3 depths, so growing legs have plenty of support and space.