This engine is driven by the temperature differential between the top and bottom plates. To make temperature differential, simply put it on a cup of hot water or on top of ice. The speed depends on the temperature differential: the higher, the faster. It can reach a speed of 180-200 RPM when in good condition. What's it for:<br> *Funny gift<br> *Kids' science project<br> *Hobby<br> *Physical/mechanical learning<br> *Put on your table<br> *You want to spend money but don't want to spend too much<br> Features:<br> * Stand: carbon steel; top and bottom plates: nickel-plated carbon steel; power cylinder and piston: glass; displacer: PVC foam; displacer cylinder wall: plastics; displacer guide: copper; flywheel, cranks, rods, shafts or so: stainless steel. Brand: DjuiinoStar<br> Model: DLTD-303<br> Speed: 60-200 RPM(revolutions per minute)<br> Start temperature differential: about 20 Celsius/68 Fahrenheit<br> Material: carbon steel, nickel-plated carbon steel, stainless steel, glass, bronze, PVC foam and plastics*<br> Overall size: 103x103x125mm/4.06x4.06x4.92in(L/W/H)<br> Size of flywheel: 87x5.8mm/3.43x0.23in(Diameter/Thickness)<br> Inner diameter of power cylinder: 15.6mm/0.61in<br> Net Weight: 238g/0.52lb<br>