Learn more about how Swagelok products can be just right for you. Search our catalogs or locate a product sales and repair center. A coupling connects two pipes. If their sizes differ, the fitting is recognized as a decreasing coupling, reducer, or an adapter. There are 2 sorts of couplings: http://valves-and-fittings53073.link4blogs.com/11583167/helping-the-others-realize-the-advantages-of-valves-and-fittings