Abstract: A connector for connecting end-to-end two spiral-wound sheet metal air ducts. The connector is an annular structure with opposite end segments, each of which presents an annular recess or groove which is open at its outer end and closed at its inner end and filled with sealing mastic there. The dimension of each recess or groove transverse to the longitudinal axis of the ducts and the connector is substantially equal to the maximum thickness of the corresponding duct (i.e., where its spiral rib is located) so that each duct has a snug sliding fit in the corresponding recess.