Universal GM-37287 consists of two shut off adapters which are connected into the PFI system fuel lines at the quick connect. GM-37287-1 connects into the 3/8" fuel inlet line and is used to shut off fuel flow during the injector leakdown procedure. GM-37287-2 connects into the 5/16" fuel return line and is used to shut off fuel flowing back to the tank during the fuel pressure test.