... quality, good finish. Super stainless steel CE certified, high efficiency, TIG welding, easy installation, reliable quality Solar Water HeaterVacuum Tube: ... Dia.: 310mm, 360mm, 500mm;Inner tank welding: Double sides argon protection welding. No corrosion;Outer tank shell: Stainless steel ... Outer tank Dia.: 420mm, 470mm 600mm;Insulation material: High pressure PU foaming with thickness of 55 mm;Stand: ...