Track Builder Speed Accessory. The Hot Wheels® Track Builder System offers the ultimate track experience for boys by allowing them to design, create and customize their very own track challenges. Using a variety of stunts, layouts and essential pieces that work together or connect to existing sets, boys can be the master of their own track. This two-speed motorized booster adds major velocity to their customized track set! If you can dream it, you can build it with Track Builder! Age from 3 years.