Compression fittings are used in plumbing and electrical conduit systems to join two tubes or thin-walled pipes together. Compression fittings for attaching tubing (piping) commonly have ferrules.
Compression fittings are popular because they do not require soldering, so they are comparatively quick and easy to use. They require no special tools or skills to operate. They work at higher pressures and with toxic gases. Compression fittings are especially useful in installations that may require occasional disassembly or partial removal for maintenance etc.