A Stirling engine is a heat engine that operates through the cyclic compression and expansion of air or other gases (working fluids) at different temperatures, thereby converting thermal energy into mechanical work. The engine principle is intuitive, educational toys and teaching experiment equipment can effectively cultivate children's interest in learning, and can also be used in classroom teaching, which is more intuitive and easy to understand. great gift for friends or family, or on your desk or anywhere Colour:Gold Material:Metal Package Contents: 1 x Stirling Engine Motor Model 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.