Couplings supplier in uae. A Pipe Coupling is a very short piece of pipe or tube having either socket or female pipe threads at one or both ends that allows two pipes or tubes of equal or different diameters to be linked together in piping or plumbing. Pipe fittings called couplings are used to extend or end pipe runs. Changes in pipe size are also made using these fittings. It can also be used to fix a pipe that is broken or dripping.