5 years & up. Build a jet car and explore how it moves! Discover how the incredible jet force propels boats, planes, and missiles with the Koontz™ Jet Car kit. Did you know that a jet engine shoots out a strong gust of air from the back end of the vehicle, which propels the vehicle forward? Made from durable, lightweight, recyclable cardboard. Includes simple step-by-step instructions and a fun activity booklet. 22 pieces.