... the international advanced level, No water inside the vacuum tube, Anti-clonglie fried tube, high temperature, good efficiency, use a super ... co-axial structureGlass material: High borosilicate 3.3 glassOuter tube diameter and glass thickness:Φ47±0.7mm; Glass thickness ... empty evacuated tubes): 260~300°cAverage heat loss: ULT 0.4~0.6w/(m2*°c)Hail resistanve: Φ25mmPressure-endure: 1Mpa Evacuated tube ...