I was told that the vent size is determined based on my audiogram to reduce occlusion.
I don’t know about Costco but through an audi, you can also have custom molds made by ReSound with Select-A-Vent. A large bore is made in the mold and then you get a tree of different interior diameter tube inserts that allows you (or your ) to play around with different vent sizes. If one really knows ahead of time what size vent is going to work best, going with the fixed diameter vent size is probably best because going with an extra large hole to take the inserts takes more supporting structure out of the mold, requires the mold to be a bit bigger than it might otherwise be with a small vent tube, etc.
You’re ignoring this member’s posts.