Many late model fuel injected vehicles no longer have a Shrader valve on the fuel rail & this makes it tough to check the fuel pressure. This special adapter fits between the fuel supply hose and fuel rail & adds a Shrader valve that can be hooked up to the fuel pressure gauge for testing. The adapter can be configured in two different ways as a strait or 90 angle and has (2) 1/8" NPT ports that can be used for the Shrader valve or fuel pressure gauge. If you don't have a fuel pressure gauge that connects to the Shrader valve, you can use fuel pressure gauge part # 100187ERL.