... SUS304-2B stainless steel, aluminum alloy; 2)Vacuum tube: 47mm-1500mm, 58mm-1800mm spaceflight vacuum heat collecting tube, large amount of heat ... no less than 95%, conduct heat fast, no water in vacuum tube, no water dirty, prevent frostbit; 4)Use automatic machinery ... with 55mm thickness. Fittings: Working station high qualityunpressurized solar water heater