... heating efficiency 2, easyly installation 3. energy-saves vacuum tube Solar Energy Water HeaterSpecification:1) Vacuum tubes: Φ47 x 1,500mm, Φ58 x ... 1,800mm, Φ70 x 2,100mm2) Vacuum tube size: 15, 16, 18, 20, 24, 26, 28, 30, 363 ... to get more information ,Packing:Standard export carton and foam vacuum tube Solar Energy Water Heater