The AP Valves OPV is an absolute must for any first stage that does not have a second stage attached. If a first stage fails the gas from the cylinder needs to go somewhere, if there is no release valve then hoses will blow at a minimum which can cause serious issues. Adding the Buddy OPV to your first stage will allow gas to escape easily and safely in the event of a first stage malfunction. The Buddy Over Pressure valve is useful for divers using independent suit inflation systems of rebreather divers whos cylinder may not require a second stage to be attached.
AP Valves OPV Features: