Abstract: A duct-connecting joint of tubular cylindrical form adapted to be telescopically engaged within the free end of a cylindrical duct having an L-shaped sealing element extending about its circumference with a base portion flush against the cylindrical wall of the connecting body and a radial flange portion biased to extend at an angle greater than 90.degree. to the base portion. The base portion is mounted within an inset zone of the connecting body so that the connecting body itself provides cylindrical guide portions on opposite sides of the sealing flange which may engage against the interior cylindrical surface of the duct to prevent destruction of the flange. Several methods are shown for fabricating the connecting body to insure that the flange is biased outward to rest at an angle of greater than 90.degree. with the base.