... ISO14001 2.DN800~4200mm 3.Material:rubber,steel 4.12 years OEM producing experience air duct joint 1:Section Drawings:1,bolt 2 ... ,nut 3,gasket 4,inner race flange 5,corrugation pipe 6,dorsal plate ... :Types and Marks:F:product code(air duct)U:product code(waveform) B:Produt code(corrugation) 6:connection sizes DN800~4200mm FUB-type ...