This very high quality shutoff valve by OmniSwivel International fits in-line between your low-pressure hose and second stage regulator (add 9/16 male or female adapters as needed for your application.) The shutoff valve opens and closes very quickly by sliding. This version is compact and the ON/OFF slide direction is field configurable. Note this version also does NOT provide positive tactile feedback when operated. The regulator first stage should also have an OPV if the shutoff is used to disable the only pressure relief path.