Salco SLV-PST-CV-1 Black Pro-Spec Threaded Emitter with Check Valve 1.0 GPH Flow Rate. The Pro-Spec Emitter offers a fully pressure compensating design that delivers uniform flow throughout a wide pressure range regardless of elevation changes and pressure inconsistencies. The Pro-Spec flow rate and flow direction are clearly molded into the diffuser cap and are also color coded or camouflaged to blend with the landscape.