Single ferrule Bite type fittings are the most widely used fittings in the world. Single Ferrule Bite Type Fittings are flarless bite type metric fittings that consist of a body, progressive ring (ferrule) and nut. On assembly, two cutting edges of the ferrule "bite" into the outer surface of the tube ensuring the necessary holding power for high operating pressures. Single ferrule bite type Couplings are best suited for steel, copper or stainless steel tubes where brazing, soldering, welding, flaring or threading is not possible or permissible.