The Apollo Expansion PEX 3/4 in. Brass PEX-A Barb Coupling is simple to install. Apollo Expansion PEX barb fittings are a key component to one of the most economical potable water piping systems. Also capable of integration into hydronic heating systems, Apollo Expansion PEX couplings must be secured into place Apollo Expansion PEX sleeves or comparable expansion-type sleeve or ring (all sold separately). The Apollo ExpansionPEX system is a comprehensive piping system comprised of lead free brass fittings, poly alloy fittings, manifolds, valves, fasteners, tools and tubing designed for implementation in water delivery systems, simple or complex.