The P-D test valve looks a lot like a real valve. That's the intention so that the air behaves as realistically as possible with the test apparatus. Each P-D Valve is fabricated with a hollow steam that connects to a "pressure tap" in the seat of the valve. For best results, you should use a P-D Valve that is the same size-including the correct seat angle-as the valve you will be running in the completed engine. Touchette says he will keep multiple P-D Valves in stock and can also fabricate P-D Valves specifically to any customer's needs.