solar collector system with SOLAR KEYMARK,CE,ISO,SGS solar collector systemMaterial:Header ... copperOuter manifold: aluminum alloy, δ2.0mmBracket: aluminum alloy, δ1.6mmInsulation: polyurethane frothing, δ40-50mmVacuum tube: tri-elements coating, copper heat pipe ... . There is frost proof liquid in heat pipe and whole system pipeline which flew by circulation pump. solar collector ...