Abstract: A seal system for joining the ends of two generally rectangular duct sections, including two frames secured to each other with a seal and attached to their respective duct end sections. The frame members each include four flange portions and four corner pieces. Each flange portion has an upstanding channel shaped leg portion and an angularly extending duct receiving leg portion. A corner piece connects adjacent flange portions to form the generally rectangular frame. The end portions of the ducts are inserted into longitudinal openings of the duct receiving leg portions. A seal, having four angular corner pieces and four linear pieces, is positioned between the frames to connect the duct sections. The overlap of the angular corner pieces and the four linear pieces establishes an effective seal to prevent air within the duct from escaping.