For a 4-year-old who's already mastered a 3-wheeler and is ready for 2 wheels, the Micro Sprite is the community's top recommendation. It's a proper 2-wheel scooter that won't embarrass them as they grow.
Most 4-year-olds aren't ready for 2 wheels, but if yours is, don't buy a cheap 2-wheeler — go straight to the Sprite. It's the scooter Reddit recommends when parents ask about stepping up.
“I too think a 2 wheeler is a bit advanced for a 4yr old, but every kid is unique. I would look at the micro sprite scooter for 2 wheels.”