58 mm Vacuum Tubes for solar wateer heater/geyser

3)        Inner tube diameter: 47±2mm

4)        Glass Thickness: 1.6mm± 2mm

5)        Thermal expansion coefficient: 3.3 x 10-6 / K

6)        Material: Borosilicate Glass 3.3

7)        Absorptive Coating: Graded A1-N/A1 (copper coating)

8)        Absorption: > 92% (AM 1.5).

9)        Emittance <8% (80°C)

10)     Vacuum: P<0.005Pa

11)     Stagnation Temperature: ≥200°C

12)     Heat Loss: < 0.8W/㎡°C

14)     Efficiency: 93% to 95%