Froth tubes tend to be clogged, so this point needs to be thought out. The ring should sit in the tube very, very tightly, there is an option to use some screws. In this case, if your tube gets clogged, you can blow into it harder, and the screws will not allow the ringlet to fly out of the tube like a cork.
Froth tubes for bubble shows can be washed, dried, etc. Below is a video on how to make a similar froth tube with your own hands.