The height of the child changes quickly and greatly. In order to perfectly adapt to this change, this bicycle seat cushion height is designed to be adjustable. By adjusting the knob, the height of the seat can be adjusted freely between 24.5""-29.5"". When children's balance ability or riding skills are not so perfect, 2 auxiliary wheels can help them to ride better while ensuring their safety. In order to keep up with the growth of kids