$7.95
Part 100139 is the pipe plug fitted to the Graco Fusion AP and Fusion PC spray guns. Graco's service manual describes it as a 1/8-27 NPT pipe plug, and the exploded parts diagram labels it simply as "Plug". Its job is the one every pipe plug does: it closes off a threaded port in the gun.
It is a small component, and small components are the ones that go missing on the shop floor during a strip-down, so it is worth having a spare before you start a service. When you are ordering from a Graco diagram, go by the part number rather than by eye, because threaded plugs of different sizes look very similar once they are out of the gun.
Genuine Graco OEM part 100139.
