Very fantastic craftsmanship， made with Metal AlloyBeing a Gift， or a Display on your desk or anywhere !The hotter it gets， the faster it goes!This low temperature stirling engine，It run on warm / cold surface， and it requires a small difference in temperatures to run.Description:Item Name: Stirling Engine Size: 102 X 102 X 125mmMaterial: Steel and GlassSpeed: up to 180-250 RPMStart Temerature Difference: 20 ℃Weight: 250gFeatures:This Low Temperature Stiring Engine could be a great gift for your friends or families.It is almost ready to run: after the installation， put it on a cup of hot water， then it will run itself.Note:Can use pencil to lubricate all the connections，other oils are not recommended.Package Included:1 x Low Temperature Stirling Engine