I just wanted to try this out. The usage is probably very limited (customized garden sprinklers/showerheads from PET-bottles).
I know that this adapter can be made with an actual gardenhose connector and some hotglue (or better yet, plumbing adapters) so it gets attached to an existing bottle cap but I just want to try this out and decided to make it available for order.
It is an UNTESTED PROTOTYPE at this point but I think I've got it all right at the first go. I'm a little worried that the printed material might not be strong enough for the thread. It might break when the cap is screwed in too tight.
The PET bottles should have a thread with approx. 25mm outer diameter and 3mm pitch (3mm between each "lap") to be compatible with this adapter. I used a "standard"(/Coca-Cola Company) PET bottle as my design reference since a lot of companies seem to use that same design.