This engine was invented by London's Pastor Robert Stirling in 1816, so it's named "Stirling Engine". Stirling heat engine is unique because of their theoretical efficiency is almost equal to the maximum theoretical efficiency, known as the Carnot cycle. Features: Stirling engine model is an educational tool that explains the theory of air expansion and contraction. By using this model, teacher can explain this theory in a much straightforward way and students will have better comprehension. Just place it on a cup of hot water, and gently flip the wheel until the wheel can run automatically. No need to fire an alcohol lamp, safer for children. The high intensity PC material is heat-resistant and harmless. Transparent body gives you a clear view on how every parts work. Fully assembled, no need to install it yourself. And the integrated ABS wheel will never deflect like the self-assembly ones. Specifications: Item Size: 10 * 11.3cm / 4 * 4.4inch(D * H) Item Weight: 132g / 4.6oz Package Size: 12.7 * 10.5 * 10.5cm / 5 * 4.1 * 4.1inch Package Weight: 180g / 6.3oz Package List: 1 * Stirling Engine Model 1 * User Manual(English/Chinese)