... .4mm 2.Outer tank:Galvanized steel,0.4mm,diamater of water tank:460mm 3.Insulation layer:50mm high dense integral ... 58mm *1800mm). Hail resistance: 25mm DescripitionStainless steel solar water heaterMaterial of out tankFood grade 0.31-0.4mm SUS304/SUS202 ... thickness SUS201/SUS202/SUS304 stainless steelStructure of tank:4 holes for air vent, overflow, water inlet and outlet, electric heaterWelding: ...