The ZENO is suitable for kids from 6 months old when it is being used at a normal walking pace. Once your child is at least 9 months old and can sit upright unassisted, they should be ready to ride in the ZENO while you go running. The seat unit is not suitable for children under 6 months. The maximum child weight limit is approx. 49 lbs. However, every child is unique and develops at a different rate. If you are uncertain whether your child is ready to ride in the ZENO please consult your pediatrician prior to running.