Regardless what runs through them, the ends of pipes and tubes often have to have some type of fitting, usually to connect it to another fitting, but often just to cap it. There are many different types of fittings, each having a different purpose. Adapters change the connection type. Couplers (or couplings) join two ends. Elbows turn corners. Other fittings include nipples, flanges and buttresses, etc. For a wider view of items used in plumbing and plumbing and piping, see other fittings.