Features: Working principle: Similar to internal combustion engine, the burning alcohols lamp provide power and heating to expand the internal gases, thereby increasing power of the internal moleculars gases on the flywheels. The engine model is make of aluminum alloys, glass, stainsless steels and wood, which is sturdys and durability. Through hands on operations, you can observe the whole process of the Stirlings engine, understand the working principle of the Stirlings engine more intuitively, and deep students' interest in physics. It have most applications, such as children's sciences projects, physics/mechanical learning, classroom demonstration props for teacher, friend, family, parent, children's birthday gift, etc. The Stirlings engine model have be assembled and can be used directly. Specifications: Material: aluminum alloys, glass, stainsless steels, wood Size: As show in the picture Output voltage: 3.0-5.0V Fuel: 95% alcohols (not included) Package Includes: 1x Stirlings Engine Motor Model note: Please allow 1-2cm errors due to manual measurement, make surely that you not mind before order. Due to difference between different monitors, the picture may not reflect the actual color.