Expansion coefficient 3.3, size range from O. D 6± 0.4mm, W. T 0.5± 0.1mm to O. D 315± 3mm W. T 9± 1.4mm, low-iron silicon sand employed in the raw material upgraded the transmittance to 92%. Widely used in solar heater, crafts and arts, lighting and solar power. We are the only authorized CSP tube manufacturer in China.