The Apollo ExpansionPEX 3/4 in. Brass PEX-A Barb x 3/4 in. CPVC Straight Adapter is simple to install and designed for the transition from CPVC pipe to PEX-A tubing. Apollo ExpansionPEX transition couplings must be secured into place Apollo ExpansionPEX sleeves or comparable expansion-type sleeve or ring (all sold separately). The Apollo ExpansionPEX system is a comprehensive cold expansion piping system comprised of brass fittings, poly alloy fittings, manifolds, valves, fasteners, tools and tubing designed for implementation in water delivery systems, simple or complex. A cold-expansion tool (sold separately) is required for installation.