These 3 simple hardwood machines explore the properties of physical science. The Wheel & Axle can operate several ways similar to a crane, the Gear moves back and forth with teeth connections, and the Pulley can move weight with its system of wheels and cord. The Gear is 15" L. The Pulley is 15 ½" H. Includes Teacher Guide. Set of 3. Ages 4 yrs. +.