... tubes, coaxialTube materialBorosilicate glass 3.3Outer tube Dia. and thicknessdia.47mm, thickness.1.6mmInner tube Dia. and thicknessdia.37mm, thickness.1.6mmTube length1500 ... ~260°Cthermal expansion coefficient3.3*10-6Pressure endurance0.8mpaImpact endurance( dia.)≤25mm hailstoneService life15year solar vacuum tubes, single target, dia. 47mm