This lead free CrimpRing (TM) coupling is used to make a straight transition between potable or radiant heating PEX tubing. This 1/2 crimp x 3/8 crimp coupling is made of lead free brass and must be joined to the PEX tubing using a copper crimp ring to form a fast, reliable, and permanent seal. It is recommended to use an electric crimp tool to make the crimp connection.