... 1,Special design for Eroupe duct flange Standard , 2,L shape, U shape, All wraped duct section with formed connections DUCT LINE-7GDF ... lock ,beaded and Duplex GDF flange,Automatically bending “L”,“U”,“Wrap”section and seam close,The customer can choice different ... input the duct data, Production line for the satisfaction of your production of qualified duct it is automatical vey well, Can help ...