European standard recommended the use of slide-on flange because of its strength. hollow double section and the ability to hide the “ L ” type corner pieces. GDF integrated flange is widely applied in Europe as a kind of quick installation duct flange. It shares common advantages with TDF flange-well seal, free of jointing and rivet. GDF flange is integrated with duct, connect with 4 bolts and special duct corner and clamp. One side forms GDF flange and the other forms clip. Or roll forming both GDF flanges in one machine as different model numbers.