Length of vacuum tube(mm):1800,1500,1600 Inner/outer diameter of vacuum tube(mm):37/47/58 Type (tube)16, 18, 20, 24, 30. Length of vacuum tube(mm):1800,1500,1600Inner/outer diameter of vacuum tube(mm):37/47/58Type (tubes): 16, 18, 20, 24, 30 Capacity (Litre): 120, 130, 135,145, 150, 175, 200, 215, 245 etc. Solar Water Heater