Phonak's Naida missing rubber from earhook external thread

Hello once more!

I’ve noticed that one of my two Naida’s, is missing something that looks like a rubber band wrapped around the start of the external thread (where the earhook screws). I got into looking that since I’ve noticed a lot of unusual whistling from that one.

I guess that there must be replacements, so… any tips?

Thanks in advance.

Here’s a picture depicting what I am describing:
hXXp://i.imgur.com/7Zaye.jpg

As one can see, there is a rubber to the right hearing aid but not on the left one also.

So, any ideas as to where one can get replacements?

I would think your hearing professional would either have them or could order them.

It looks like some sort of sealing gasket. Since you mention feedback, perhaps the gasket is to provide a good sound seal for the receiver.