Features: brand new and high quality This is traditionally known as an external combustion engine in contrastto an internal combustion engine where the heat input is by combustion of a fuel within the body of the working fluid. As in all heat engines, the normal cycleconsists of compressing cool gas, heating the gas, expanding the hot gas, and finally cooling the gas before repeating the cycle. A Stirling engine is a heat engine that operates by cyclic compression and expansion of air or other gas, the working fluid, at different temperature levels such that there is a net conversion of heat energy to mechanical work. This good-looking Low Temperature Stirling Engine could be a great gift for your friends or families or yourself. Durable, well made, sytlish, and adjustable.Very fantastic craftsmanship, made with Metal Alloy. Specifications: Material: Metal Size: 9.8x9.8cm/ 3.9x3.9 in Package Includes: 1x Stirling Engine note: Please allow 1-3cm error due to manual measurement. pls 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.