A filament filter designed to connect to a PC4-M10 coupler and PTFE tube.

The opposite end has a chamfered insert to help prevent bent/twisted filament from jamming up the system. A second variant of this back piece is designed to be mounted to a surface with screws or adhesive.

A small chunk of foam fits inside the cavity. Just cut one from a new and clean sponge. Ram a pointed end of filament through it a few times once in place to make a hole and remove any debris. Then attach this to your PTFE tubing.

If you consistently have trouble getting the filament through into the coupler/PTFE tubing, try chamfering the end of the PTFE tubing.