... solar keymark 2.Anti-freezen & pressurized 3.10 years warranty Vacuum tube solar collecotr a. Module design, arbitrary combination, harmonize with ... 150W,Working pressure,4Mpa,welding pressure 4MpaDust Ring GasketSilicon Rubber Vacuum Tubetri-element tube,High boron and silicon content 3.3 ... Structure,Gradual change SS-AL-Nx/Cu selective absorption coating,Vacuum Degree,P<=5*10-4,Service Life,10 years ...