Description: Very fantastic craftsmanship, made with metal alloy and acrylic After the installation, put it on a cup of hot water, then it will run itself. The hotter it gets, the faster it goes! Being a gift, or a display on your desk or anywhere! Great gift for your friends or families. About Stirling Engine? A stirling engine is a heat engine that operated by cyclic compression and expansion of air or other gas (the working fluid) at different temperatures, so that there is a net conversion of heat energy to mechanical work. Note: Cup is excluded. Specification: Item Name: Stirling Engine Model Material: Alloy flywhhel, Acylic Base Size(D*H): Approx. 9*15cm / 3.54*5.90inch Speed: Up to 180-250 RPM Start Temerature Difference: 20 ? Weight: 302g Package Includes: A Low Temperature Stirling Engine Model