Stirling refrigerator does work by the thermal expansion and contraction of gases as they change between hot and cold environments. Compared with traditional refrigeration technology, the advantages of free piston Stirling technology are High efficiency, low noise, low vibration, Oil-free operation, long life and 100% natural refrigerants to support sustainable environmentally-friendly operations. And also Stirling Refrigerator can ignore operating angle, 360° operating is OK. It can precise control refrigerating capacity out freely.