solar energy water heater 1.CE mark 2.Adjustable frame,easy and safe to use and protects freezing 3.Good quality solar energy water ... thickness 2.Inner water tank:SUS304-2B stainless steel(food class),0.4mm thickness 3.Vacuum tube:high quality borosilicate glass ... ,AL-N-AL coating,1.5mm thickness4.Heat Preservation:Polyurethane Foam,50mm thickness,keeping hot wahter ...