... heater*CE,ISO9000,ISo14001*high efficient vacuum tube*rapid heating transfer High efficient vacuum tube solar collector: size: 47mm,1500mm,/58mm ... according the tank capacity,copper pipe: material purple copper,glass tube: high borosilicate 3.3, thickness: 2.0mm,insulation: rock ... hot, more high efficient, and water more clear,because no water in tube so can work in bad weather condition. more ...