Ferrule Compression Fittings: Ferrule fittings consist of components such as Nut, Back Ferrule, Front Ferrule and Body. Ferrule is also known as compression ring or olive. The nut is threaded onto the body, and the ferrule is placed over the tubing. When the nut is tightened onto the body, it compresses the ferrule onto the tubing, creating a tight seal. Strong leak free joint is formed by attaching the tube with compression fittings by swaging.