... Deno three-target solar vacuum tube with CE1, Three-target Solar vacuum tube for solar water heater2, ISO900:2000, CE certificate3, 0.91 ... 5, The inner tube is also made of quartz sand, but it is coated with a special selective coating with strong heat absorption and ... , So it also can operate in low temperature and low sunlight medium.MODELITEMSGB(single target)ConfigurationDouble-layer concentric ...