solar vacuum tube 1) high quality and reasonable price 2) environmental friendly 3) nice design 4) ISO9001:2000 StructureAll-Glass Double Tube Co-Axial StructureGlass MaterialHigh Borosilicate 3.3 GlassExternal Pipe Diameter & Thicknessdia.=47±0.5mm &=1.6mm, dia.=58±0.5mm &=1.6mm,dia.=70±0.5mm &=2.0mm, Internal PipeDiameter & Thicknessdia.=37±0.5mm &=1.6mm, dia.=47±0.5mm &=1.6mm,dia.=58±0.5mm &=1 ...