Skylight Evacuated Tube Specifications: 1. Length (nominal):1800mm/1600mm 2. Outer tube diameter: 58mm/47mm 3. Inner tube diameter: 47mm/37mm 4. Glass thickness:1.8mm/2.0mm 5. Thermal expansion: 3.3x10-6í¦C 6. Material: Borosilicate Glass 3.3 7. Absorptive Coating: Graded Al-N/Al 8. Absorptance: v>93% (AM1.5) 9. Emittance: