A fitting is a detachable piece of pipe or tubing that either connects to another piece of pipe or tubing or connects two such pieces. Fittings are generally used in mechanical and plumbing operations for a number of different purposes. There are many different kinds of fittings, made from a variety of materials: some of the most common types are elbows, tees, wyes, crosses, couplings, unions, compression fittings, caps, plugs and valves. http://www.vitechdevelopment.com/pipe-fittings/