I have the old school military (Jerry Cans) fuel cans. The one the lid stays connected to the can via a chain. The threads being 2" NPT. That use the type of large neck filler that has a large rubber seal between two washer type compression rings. They seal by rotating a cam lever where they go into the can. The ones that are hard to come by now days.
Anyway, I found a seller on eBay that had threaded nozzles. Smaller filler tubes, but hey, it's something one would expect to suit the need.
I bought two of them. I expected them to be made in USA for the price. Nope, made in Taiwan. Not worth $17/ea. For that matter, not worth 1/4th the price I paid.
The threads are close enough to thread in, all along, feeling as if it wanted to cross-thread. Once it was to the washer....to hand tight, the (gummy bear) washer squeezed it's way out of where it needed to be to make a seal.
Any that have the black filler cap, I would say they are the same as what I purchased.