The female thread works with a US garden hose (0.75 11.5NH seems to work well). The male thread is BSP 0.75, which I guess is used on some sprinklers in the UK and/or EU?
TBH I'm not entirely sure if this is useful for any more than one particular sprinker model, so I'm posting this as a remix of that model in case it's really only useful for that model. It may be useful for other stuff, but YMMV.
The .f3d is included in case you want to make the inlet or outlet longer or shorter.
I recommend printing at 0.15mm layer height so the threads have a better chance of working.
The intended printing direction is the small end down, so that the interior of the bigger inlet end can have a flat surface for a washer (if desired).
This seems to work well enough without a washer for a sprinker, since a little bit of a leak isn't necessarily a big deal for a sprinkler. For use as a coupler (assuming BSP 0.75 hoses are even a thing), presumably a washer would reduce leaking.
The only potentially interesting thing about the model itself is how the outlet thread transition to the sorta-conical portion works - it starts at the exact profile of the upper part of the outlet threads, so the sorta-conical portion isn't perfectly conical etc. This is intentional to help it print properly outlet-end (BSP-end) down while preserving full strength.
The BSP threads seem to work ok with 3D printed BSP threads, though in that usage they can be a little tight. A wrench can be used on the adapter if printed from PETG and you're careful not to squish it too hard. The US garden hose inlet end works with the one garden hose I've tried so far (without a washer, so far).
The author remixed this model.