1.CE,ISO,CCC,CQC approved 2.Capacity:5L,8L,18L,36L,55L 3.Especially for non pressure system Assistant Tank /Auxiliary tankInner Layer MaterialStainless steelInner Layer Thickness 0.4mmOuter Layer MaterialStainless steel or Color steelOuter Layer Thickness165 assistant tank 0.4mmInsulation MaterialPolyurethaneInsulation Thickness15mm assistant tank for solar water heaters