After using a funnel to try and fill my 30ml dropper bottles (like the one in the pictures) with paint, it went everywhere due to air locking. Also, the paint had particles in it so it needed filtering. I used a paper filter which worked, but was oversized for the amount of paint needed and the size of the funnel I was using.

So I created this thing.

A funnel that allows the bottle to breath as it gets filled and can filter the paint (or whatever you are putting into it) if needed. The funnel itself is as simple as push it in, fill the spout, job done. 

To use it as a filter I didn't like using the paper filter for approx. 30ml paint and then throwing it, but its a single use thing .. what's a numpty to do...buy some pipe filters from AliExpress and make the filter sit in the funnel, of course!

Seems there are two types, a flat one (that's a filter, but not very fine) or the bucket shaped one (much finer filtration) and this thing can take them both, even together if you wish.

HARDWARE

Hardware that you will need to use it as intended are three M3 heat inserts and three M3 pins (I used M3 x 6 but it can take up to 8mm in the blind holes so it can probably take 10mm pins with the filter and top on it). That's it.

PRINTING

I printed it with PLA+, tree supports, brims (for bed adhesion), 3 walls and 8% infill (I don't think there was much infill, if any) and in the orientation shown in the Orca Slicer pictures.