EDIT: I just uploaded a new version with both parts in one, that i printed in TPU. Because the PETG part tends to snap pretty easily.
Print the outer part in TPU 95-ish-A. You want a little bit of flex, but not enough for the piece to wriggle.
Print the inner part in PETG.
Takes quite a bit of pressure to pressfit them together. Will sit very tight in your Ello Duro or any other tank with a 12.6 mm opening.
Both are designed to be printed at 0.2 layers.
The author marked this model as their own original creation.