The ultra-low temperature refrigerators are also called ultra-low temperature storage boxes, ultra-low temperature freezer, ultra-low temperature freezing box, etc. The common -60 to -85 degree low-temperature refrigerators are suitable for freezing and refrigerating tuna, fish, shrimp, sea cucumber and seafood. It is also used for low-temperature testing of electronic devices and special material, and storing of plasma, biological materials, vaccines, and reagents. There are also extreme freezer refrigerators with -40 degrees, -60 degrees, -86 degrees, -120 degrees, -136 degrees and -160 degrees. For these refrigerators, they are used to preserve drugs, vaccines, enzymes, hormones, stem cells, platelets, semen, transplanted skin, specimens taken from the human body, germplasm banks of plant seeds, gene cloning libraries and some important biological and chemical reagents. Moreover, the low-temperature refrigerators mainly work for low-temperature experiments and storage of special materials such as scientific research, preservation of medical supplies, biological products, ocean products, electronic components, and chemical materials. And mostly they are used in hospitals, universities, research institutes, and industrial storage.