As best I can tell. The OD of the thread measures 6.3mm, so basically 1/4"
Thread pitch, on imperial the thread gauge closest match is 25G, whatever that means.
Metric pitch it's exactly 1.0mm
Inside the jet. This jet must be about 18 years old ! lol, I assume they are still the same though. This one had a 4mm hosetail on the right hand piece in the photo.
