... &ISO9001 4.Manufacturer more than 8years solar vacuum tube1,vacuum tube length:47/1500mm,58/1800.2,vacuum tubes:15pcs,18pcs,20pcs,24pcs,30pcs3 ... tube58-1800mm co-axial structure high borosilicate 3.3 glass vacuum tube with tube wall thickness of 1.6mm.Inner tank materialSUS304-2B ... the water is full,it will close the valve automatically Three target solar vacuum tube