It has all kinds of styles such as children's bicycles, field bicycles, racing bicycle and so on.

I did come across a document (PDF) from the U.S.Consumer Product Safety Commission that suggests that ages four and five are when it's appropriate for kids to "ride small bicycles."

Its hatch is bigger than most and its rear roofline is fairly high, so it accommodated my sons' two small bicycles with space to spare — a big surprise.