MNPT 90-Degree Male Elbow is simple to install. MNPT PEX-A Barb Brass 90-Degree Male Elbow Fitting Brass PEX-a Barb x 1/2 in. A cold-expansion tool (sold separately) is required for installation. Apollo ExpansionPEX barb fittings are a key component to one of the most economical potable water piping systems.