This mechanical EFI fuel pressure gauge reads up to 100 psi and comes complete with attaching adapter. It’s manufactured by Marshall and made in the U.S.A. The adapter is CNC-machined for precision fit and leak-free performance. It attaches directly to the schrader valve outlet on the factory GM fuel rail. The front side of the fitting accepts a standard 1/8″ NPT fitting, which matches the outlet on the very distinctive engine-turned face, liquid-filled 1-1/2″ fuel pressure gauge. The gauge is liquid-filled to reduce needle vibrations, insure accuracy, and is very durable. Now you can tell if you have a fuel problem by simply checking the fuel gauge at the end of the fuel rail. It’s small, so it doesn’t interfere with any under-the-hood modifications. This kit is easy to install and adds a high-performance look under the hood.