Duct Seals are unique for several reasons. The expandable seals are colour coded for easy recognition. They are made from a specially formulated polyurethane designed to give maximum sealing and expansion properties. While a single seal is difficult to align properly, a double seal is expensive. The DCD unit has a single seal, but supports it with an alignment washer. Economical but effective. All seal sizes fit over the same Handle Assembly and changing the size of seal used is a breeze. Just unscrew two nuts, slide off one Seal Kit and slide on the next one. The end of the unit is fitted with a quick release coupling. Each Seal Kit comes complete with the polyurethane seal, two compression washers and one stabilizing washer. Just order the size of seal you need plus one Handle Assembly. Next time, just order the new size of seal you need.