Below I have copied/pasted my reply of a couple of months ago on another thread, which may be of help to you (I should add that domes are highly elastomeric, and so demand more info if your Audi makes a knee-jerk “they won’t fit” comment)
Here is an unusual choice regarding domes, which certainly isn’t appropriate for everyone (or perhaps anyone!):
I use Phonak domes with my Oticon Agil Pro RITEs. The domes I use are the Phonak so-called closed domes. I say so-called because they have two small vent holes, so that shows that I don’t understand the open and closed nomenclature as well as I thought I did. These domes have one “cone” (not two “cones” like Oticon and Phonak Power domes), two small vent holes as mentioned, and the tip has a sort of little loop that forms two sideways-pointing holes that open the passage from the ear canal to the receiver wax guard.
Even though I probably should be using power domes, not only do I find the “head in a bucket” effect unpleasant, but I just plain can’t hear as well (even though my Audi says the HAs are programmed for closed power domes). Also, the Phonak single-cone closed domes are more comfortable for me than two-cone power domes in any size. Tulip domes are also comfortable, but they don’t work for me for other reasons. Finally, the Phonak “sideways-holes” design seems to do a better job of delaying wax accumulation in the wax guards compared to the Oticon “multiple-micro-holes” design.
The price I pay for using the Phonak domes is, as you might guess, feedback. However, I have only occasional solid-object-reflection feedback. With the Phonak “closed” domes I can detect some feedback in a few situations where there would be no feedback with the completly closed two-cone power domes, but this slight disadvantage is more than offset by the previously noted advantages.
BTW, having trialed both Oticon Agil and Phonak Audeo HA’s (using the same domes), I can say that the Phonaks do a better job of feedback cancellation, but their well-known tendency to switch programs (and perceived amplication levels) at odd and annoying times (e.g., while driving, as various posts have noted) was a big negative factor for me.
(Hz) L(dB) R(dB)
250 40 50
500 55 65
1K 55 60
2K 60 60
4K 70 70
8K 90 100
L: 88% SDat80dB
R: 64% SDat85dB
L&R stapedectomy <!-- / message -->