They are a great way to ride with young children. My son was 3 when he first started riding on one. He out grew it at around 7. Probably could have squeezed one more year out of it. They are a great way to teach kids how to ride in traffic. I would go with a single speed model. I see no point in having gears on them.
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The moral arc of the universe is long, but it bends towards justice. M.L.King