... 1.color paint steel material,unpressurized 2.ISO,CCC,CE,5years warranty,OEM ... 1.1.6mm thickness borosilicate glass 3.3 2.AL-N-AL or Cu-AL-SS coating ... Inner tank:0.5mm thickness SS304 stainless steel 2.Outer tank:0.4mm thickness SS202 stainless steel ... 5mm thickness; 2.Angle of stand:18°,20°,38°,45°Working Principle:There is water in the vacuum ... the air. Related products: low pressure solar water heater