... Anti-freezen & pressurized 3.10 years warranty Solar thermal vacuum tube solar collecotr a. Module design, arbitrary combination, harmonize ... and long life7) Significant advantages over flat plate8) Easy plug-in installation9) Suitable for mains pressure water10) Corrosion ... ,4Mpa,welding pressure 4MpaDust Ring GasketSilicon Rubber Vacuum Tubetri-element tube,High boron and silicon content 3.3 ...