Budding engineers discover how machines make work easier. Features 55 sturdy plastic pieces?enough to build all 5 models at once. Activity Guide contains child-friendly directions for assembling and using a lever, wedge, pulley, inclined plane, and wheel and axle. Includes 8 rubber bands and 4 weights to explore effort, force, load, motion and distance. Largest machines (pulley and inclined plane) measure 5?"L x 5?"W x 12"H each. Ages 9 . Set of 63.