... :1.volume of storage tank:120L,180L,240L,300L2.pressurized water tank: insulating layer,polyurethane foaming ,thickness:55mm outer shell ... pressure:6bar,test pressure:12bar3.dust ring gasket :EPDM4.evacuated tube:three-target tube,high boron and silicon,content 3.3,structure ... both in flat and inclined roof,and can be use with an auxiliary electric booster as to provide hot water without sunshine. ...