UPDATE: To include a plain version to fit the std plastic filament feeder.

The upgrade filament feeder I bought didn't come with an inlet adapter but did have an M6 thread. So I made a filament guide with an M6 thread & printed it in Taulman 3D Nylon 645 as nothing tends to stick, not even to the bed most times!

0.3mm nozzle @ 0.1mm layer height, print time 23 mins. @ 20mm.sec max.
35% infill for Nylon 645

Maybe an addition to this is put a pipe cleaner in the inner cone to remove dust as it feeds??
My printers are i3 Pro B's.

Depending on material & settings you might need to remove a small lump from the inner part of the cone. I didn't need to chase the thread with a die, it just fitted straight off the printer.