Paper pots made from old newspaper are a great sustainable device for the hobby gardener to seed one's plant in. Whilst making the pots goes easy and quick, filling them with potting soil can be fiddly when using smaller sizes. That is where a funnel is usefull.
I bought a "Paper Pot Maker" by Burgon and Ball. Mostly, because it offers three different sizes in one pack, but this really does not depend on any special product. Just the size is perfect for the middle size of this: https://www.burgonandball.com/products/paper-pot-maker . I made this funnel for the middle size but it works great for the larger sizes as well. As this is a simple SCAD file, adapting sizes will be an easy task, should there be a need.
(Edit: TinkaSil reported that this fits on paper pots made with a thingiverse paper pot maker, cf https://www.thingiverse.com/make:627039 and https://www.thingiverse.com/thing:1132645 )
As you can see from one picture, I have found it very usefull for a seed tray as well: Filling a whole tray with potting mix does not need a funnel, but refilling after some plants have been removed, this turned out to be very usefull (here: QuickPot for 56 plants http://www.herkuplast.com/de/programm/QuickPot/Standard.html ).
I am very content how this turned out. Cura says mine took about 17m or 51g of filament. So this would be suitable for a 50g test package of filament.
DAS FILAMENT PETG
This does not need support nor high resolution, just print it upside down. I chose to print it with a brim, which I did not care to remove for the pictures above or for everyday work.