Features: A Classical Stirling Engine Model: Made of quality metal material, clear body gives you a clear view on how every parts works. Working Principle: It outputs power through a cycle of cooling, compression, heat absorption, and expansion of the air in the cylinder. Highly Performance: It would observe and know the operational process and more intuitive understanding of the operating principle. Educational Toy: School classroom or laboratory experimental teaching aids, the great gift choice for students, teachers, children. Easy to Operate: Fill the alcohols burners with your 95%alcohols and light it. Let the light burn the round ended cylinder for about 30 seconds, then give the wheel a gentle push. Specifications: Material: Metal Color Options: 4 Colors are Available as Shown in the Picture. Package Weight: approx.450g Size: approx.17.5x9.5x11.5cm/6.88x3.74x4.52in (More Size Detail, Please See Photo.) Package Includes: 1Pc Stirling Engine Model note: Please allow 1-2cm error due to manual measurement. Please make sure you do not mind before you bid. Due to the difference between different monitors, the picture may not reflect the actual color of the item. Thanks!