1 The vacuum tubes absorb the solar energy and transfer into the heat energy,then pass it to the U pipe,it can get high temperature. 2 There is no water in the vacuum tube,so the tube will not break in the winter. 3 It is steady and credible. 4 It can be combined with the architecture perfectly. 5 It can be combined with existing pipeline. 6 It can still operate in the event of occasional tube breakages. The details of material: Outer tank: Alnico1.5mm Manifold:22mm thickness 2mm U copper type: 8mm thickness 0.6mm