This fitting has an OEM 1/4 inch Schrader connection which is the most common connection size for almost any fuel pressure test kit（works on fit for Ford 6.0L diesel engine 2003 2004 2005 2006 2007 2008 2009 2010 ）<br> Low Fuel Pressure is one cause of premature 6.0L injector failure- adapter makes checking fuel pressure easily<br> Note:<br> 1. Remove the factory fuel pressure test plug (Allen head) located on the secondary fuel filter housing on top of the engine<br> 2. Screw in the adapter fitting and tighten lightly with a wrench to seat the O ring<br> 3. Attach your fuel pressure gauge to the Schrader fitting and finger tighten<br> 4. Start the engine and carefully check for leaks<br> 5. When finished, remove the fuel pressure gauge and adapter fitting and re-install the factory Allen plug<br>  Always wear safety glasses when working with pressurized fuel!<br> Please don't forget to lube the o ring before installation<br> Do not leave the fitting installed. The valve will leak and kill your injectors.<br>