My daughter is of medium height and medium weight and had to just before their 3rd birthday wait until it necessary size and strength for this impeller reached. Driving they had then relatively quickly it already could soon lift both feet off the ground and I bought her a real bike shortly before her 4th birthday. The transition went smoothly (immediately without support), only the brakes took a while - the handbrake of Pukys they had at this time can not operate and Ruecktrittbremse was her unheard. The impeller is still in use and seems downhill easy to make more fun than normal.
All in all I would recommend this very wheel, but would forego the brake.