Material High boron silicon glass(Special Hard) Model Glass Vacuum Tube Glass Tube diameter 47mm Thickness of Vacuum 5mm Wall Thickness   Single Tube Weight 1.5 kg High vacuum, long-term stability 5*10 pa Absorber Material Aluminum Coating Aluminium Nitride Absorption Coefficient  a>/ 0.94 Wind resistance 30 m/s Freezing Tolerance -30 C Hail Resistance 25mm hail Insolation Temperature 250 C Start-up Temperature \<25 C