Modified from the original version:

• made the funnel shorter, and the angle more steep
• added about 2cm space for the filament to pull out
• increased length of the leash

Since the filament has a slight curve it will be pushed back if you just push the PTFE tube in.

So to use it properly, you must push in the filament first, then shove the PTFE tube in until you have a tight seal.