5-in-1 engineering kit: build five, fun functional models including a rescue copter, aircraft launcher, hand mixer, spinner toy, and centripetal force machine Learn about gears and transmissions as you assemble and experiment with your models--no batteries required! Includes a 24-page, full-color manual with clear language, simple step-by-step illustrated instructions, and scientific explanations. Entertaining, affordable, and educational purchase--great birthday gift! For ages 6 and up