G'day,
Just to clear up any confusion the black o ring type thing is meant to be pressed into the inlet needle housing separate of the needle. I usually use a small pin punch and press them in firm. The needle then pushes into the small hole in the o ring and cuts off the flow. The inlet needle needs to move separately to the 'o' ring (or seat).
I hope this clears up confusion, rather that confusing you further!
Regards Jay
