Flared connectors should not be confused with compression connectors, since they are generally not interchangeable. Lacking a compression ring, they use a threaded nut instead. A flaring tool is used to enlarge tubing into a bell shape matching the tapered, projecting conical shape of the flare fitting. The flare nut, which has previously been installed over the tubing, is then tightened onto the fitting. Typically made of brass or plastic, stainless steel or other materials may be used.
Although flare connections are labor-intensive, they are durable and reliable. Considered more secure against leaks and sudden failure, they are used in hydraulic brake systems.