... . Super stainless steel CE certified, high efficiency, TIG welding, easy installation, reliable quality Solar Water HeaterVacuum Tube: ... 310mm, 360mm, 500mm;Inner tank welding: Double sides argon protection welding. No corrosion;Outer tank shell: Stainless steel, Al- ... Zn zinc steel sheet, or Anti-corrosion Fluorine carbon steel plate;Outer ...