... long as more than ten yearsVacuum tube: Φ58*1,800mm double-vacuum solar collector tube, the product is a high-tech ... leakage, aging resistance, high efficiency, vacuum super heat conduction, one-way heat transfer, etc.Volume (L): 160 to 350LNumber of persons ... /Φ58--45° Shenzhou 7 Light Gathering Series 30GS18/Φ58--45° double vaccum solar energy heater