... yearsVacuum tube: Φ58*1,800mm double-vacuum solar collector tube, the product is a high-tech product with proprietary intellectual property rights ... the tube, scaling resistance, no tube explosion, no water leakage, aging resistance, high efficiency, vacuum super heat conduction, one-way heat transfer ... ° Shenzhou 7 Light Gathering Series 30GS18/Φ58--45° double vaccum solar energy heater