PEX coupling connects PEX pipe to PEX pipe and are for use with any SDR-9 PEX tubing that meets ASTM 876/877.  These fittings can be used with either the cinch clamp or a copper crimp ring for a secure connection.  PEX fittings are certified by CSA, IAPMO, UPC and are NSF 14/61.  Also known as crimp fittings, insert fittings, brass pex fittings, barbed fittings or F1807 fittings.