The gun needle is the main mechanism in the airless spray gun that acts as an on/off mechanism. Generally if your spray gun spits paint after the trigger has been replaced, the needle needs to be replaced.
The G10 spray gun was a common airless spray gun that was included with a variety of airless paint sprayers, including the SW317/419/423, ED2005/2205, and many Amspray models.
Part #: 944-620
Part #: 0149368