A compression fitting is a type of coupling used to connect two pipes.  The ferrule is attached to the nut, will release and grip onto the tubing when tightened.  These Aero Mist brass fittings are used to couple copper and nylon tubing.  The brass compression fittings do not require flaring, soldering or other tubing preparation.  These 1000 psi brass fittings are rated for low or high pressure misting and fogging systems.  3/8" compression fittings for copper or nylon.