The GT Bicycles Girl's Siren 20" Bike is built around what GT calls the Legit Fit system. The Legit Fit system enables GT to build kid's bikes that have narrower cranks, proper gearing and improved body positioning. All with the benefits of optimizing pedaling, balance, and speed right from the start. Even better is that it's a system that works for kids of all ages no more needing to "grow into" a bike. The GT Bicycles Girl's Siren 20" Bike is designed to make your little one feel like a big kid.