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.