Vacuum Tube Solar water heater: high efficiency, TIG welding, reliable quality, good finish, competitive price ... Features of our vacuum tube solar water heater:CE certified, igh efficiency, reliable quality, inner tank TIG welding ... tank Dia: 310mm, 360, 500mm;Inner tank welding: Double sides argon protection welding. No corrosion;Outer tank shell: Stainless steel, Al ...