What is this!

[cmandp]

Looks like it would go in the inlet/supply connection as a large debris strainer or something.

 

[shinnen]

Have you run the pressure washer since it was returned?

I have not.

 

[racecougar]

I have not.

Might be a good idea to check it out.

 

[The Cobbler]

what's the OD size? wondering if it's a backflow preventer for the water supply side

 

[shinnen]

what's the OD size? wondering if it's a backflow preventer for the water supply sid

Well, the maximum OD would be the tail ... 16mm.
The opposite end with the O ring it 12mm, including the O ring.
The shaft, which is and X shape (looking down on it) is 5mm across
And the centre 4 protusions are 10mm tip to tip
The whole thing is only 33mm long.

 

[shinnen]

Might be a good idea to check it out.

It seems to work allright. The stream however seems to shoot off to the side somewhat, like you would get if you touched it's edge. But when I remove the piece that goes from the wand (see image) to the hose, I get a nice long staight stream.
P.S. My wand leaks inside, at the piece which moves when the trigger is squeezed.