Features: Easy to Operate: Just place it on a cup of hot water, and gently flip the wheel until the wheel can run automatically. Superior Performance: By operating the engine, children would observe and know the operational process and more intuitive understanding of the operating principle of Stirling engine, deepening interest in physics. A Classic Stirling Engine Model: Made of premium metal, Transparent body gives you a clear view on how every parts work. Safe for Children: No need to fire an alcohol lamp, for children. Fully assembled, no need to install it yourself. Great Educational Toy: classroom or laboratory experimental teaching aids, the gift for students, teachers, children, friends and colleagues. Specification: Model: D3 Size: 9.9 x 11.4cm() Color: Gold Material: metal Package Contents: 1 x Stirling Balanced Engine Only the above package content, other products are not included. Note: Light reflection and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.