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, and the high intensity PC material is heat-resistant and harmless. Transparent body gives you a clear view on how every parts work. Safe for Children: No need to fire an alcohol lamp, safer for children. Fully assembled, no need to install it yourself. Great Educational Toy: classroom or laboratory experimental teaching aids, the best choice gift for students, teachers, children, friends and colleagues. Specification: Model: D1 Material: Metal, PC Size: 9.9 x 9.1cm(DxH) Weight: 133.5g/4.7oz Package Size: 19 x 10.8 x 13/7.5 x 4.2 x 5.1in Package Weight: 216g/7.6oz Specification: 1 x Stirling Engine Model