I modified IRobertI's Alternative feeder V2 to work with 1.75mm filament and a 2/4mm (ID/OD) bowden tube. Only the modified parts here, you also need to print the rest of the parts from: https://www.youmagine.com/designs/alternative-um2-feeder-version-two Instead of a grommet i use a bowden coupling and a small piece of bowden tube at the entry point for the filament.The bowden tubes should end in the 4mm holes flush with the printed surfaces, and you should countersink the ends to ease the insertion of filament.If you want to use it as a second feeder as on my pictures you need to print all the parts mirrored.