This specialized tool connects in-line between the 2nd stage regulator and the LP hose, allowing adjustments to the "cracking pressure" of your second stage. Using the included pressure gauge the intermediate pressure (IP) of the first stage may be checked. Then a flat blade or hex key (you must have configured the tool for one or the other before pressurizing) can be inserted in to the 2nd stage to allow the orifice to be turned to find exactly the proper adjustment for the 2nd stage air inlet(cracking pressure). This dual tool has 0.032 inch flat screwdriver like adjusting tip, which fits most slotted regulator orifices and also a 5mm hex key adjusting tip (just reverse the tool.) We use this tool in our own service department and our service tech tells us the quality is excellent but notes that while this tool works with most adjustable second stages, and nearly all modern designs including all the regulators we sell, it does not work with every brand of second stage.