Simple adapter vor the [3D Solex PFTE Coupler](https://3dsolex.com/umo/2410-tfn-ptfe-coupler-umo-7072482000512.html) to better fit it into the Ultimaker Original print head. As you can see in the images, the 3D Solex coupler is a bit smaller where it is inserted into the wooden part of the print head. That's why it can easily be tilted which causes friction on the filament. This adapter perfecty fits the 10 mm diameter hole in the wooden part in the print head and is a bit longer than the original part is. This makes it easier to insert the bowden tube into the coupler.