... :rubber,steel 4.12 years OEM producing experience air duct joint 1:Section Drawings:1,bolt 2,nut 3,gasket 4 ... plate flange 7,inner sleeve pipe flange 8,outer sleeve pipe flange 9,outer sleeve pipe 10,o-ring seal 11,inner ... (corrugation) 6:connection sizes DN800~4200mm FUB-type air duct joint