The Anest Iwata Air Valve Seat Set 93843530 is designed specifically for the W400 series spray guns, the WS400 & LS400 Series 1 spray guns as well as the LPH400 spray guns. This part sits at the front of the spraygun giving an airtight seal at the front where the needle exits behind the trigger, if your gun is leaking air at the front, there's a good chance this is the problem.
