An adjustable or variable joining device (such as a fitting or connector) used to connect a duct (such as pipe or tubing) having a range of shapes, sizes and thread styles to an object (such as equipment, a container, or another length of pipe or tubing). In various embodiments, the device may generally comprise a sealing member, a support assembly, and a support plate. The sealing member is adapted to seal the duct to the device by elastically expanding to fit around the exterior surface of the duct. The support plate, which is placed adjacent to the interior surface of the sealing member, protects the sealing member and prevents it from collapsing under thrust loads. The support assembly is positioned on the outside of the sealing member and assists in operatively holding the sealing member in place. The device may also comprise a casing member, which encloses the above members.