Well…. For a long time I used standard Caps to avoid my filament from getting moist inside the PTFE Tube.

But after cutting away many meters of “bad” Filament I have to accept that this is not the solution for difficult materials like TPU, PA, PETG, …

So I used my M10 Drybox Passthrough to make all the Ends run into a box filled with silicagel. This works very good!

https://www.printables.com/model/72934-m6-m10-dry-box-sealed-passthrough-screw

Additionally I created this smaller container which can be filled with some Silicagel. It also works a lot better than the normal caps. But of course you need to replace the silcagel from time to time. (I use my prototype since 1 month and did not need to do that yet)

In the file there is an optional TPU O-Ring included. I did not need it but if you want to go for security you might want to install it.

have fun and keep printin!

PS: This model is for 1,75 mm Filament in a 4 mm outer Diameter PTFE Tube and you will need M10 push fittings.