BUILD YOUR OWN ENGINE KIT – The Build Your Own Model Engine Kits from Machine Works make excellent gifts for vehicle and model enthusiasts who like creating and learning about mechanical systems and engineering. Requires 3 x AA Batteries (not included). DIY KITS FOR ADULTS AND KIDS – This functional model of a 4-Cylinder Internal Combustion / Electric Hybrid Engine is the perfect activity for both children (over 10 years) and adults to build together. You will also need 3 x AA Batteries to power the motor. DISCOVER & LEARN AS YOU BUILD – This Hybrid Engine is a simplified Replica of a 4-Cylinder Internal Combustion / Hybrid System. It demonstrates the internal combustion, eco mode and electric-only operations of a typical Hybrid System. INCLUDES OVER 100 PARTS – This 100+ piece kit for kids and adults is enjoyable to construct and includes all of the tools you'll need to complete the operating model. The Fully illustrated step-by-step Instructions guide you through every stage of the assembly process. Each component is clearly identified, and each function explained. PRODUCT FEATURES - The transparent engine case of the finished model means the moving parts are clearly visible when it’s operating, allowing you to see the interaction of the crankshaft, pistons, and valves, as well as illuminating spark plugs.