Abstract: A tubular body is provided having first and second ends and the first end includes structure for connection with one end of a tubular duct while the second end of the body defines a peripherally extending and outwardly opening groove. A pair of semi-annular sheetmetal sections have their inner peripheral portions edgewise engaged and seated within the groove at the first end of the tubular body and the semi-annular sections are of slightly greater than 180.degree. in angular extent and have their opposite ends overlapped and joined together. The semi-annular sections, after being joined together, define an annular collar mounted on the first end of the tubular body against removal therefrom and the side of the annular collar facing outwardly of the first end of the tubular body has an annular resilient gasket mounted thereon whose outer side includes an adhesive coating for adhesive securement to a duct wall about an opening formed in that duct wall.