it all depends on the person, the size of your ear canal, the type of hearing loss, and how bad the hearing loss. We are all different and have different needs and requirements when it comes to ear molds and domes. Most of my hearing aids life I have worn ITE (in the ear) hearing aids, nothing behind the ears. I have also worn hearing aids with domes, and now hearing aids with custom ear molds. My ear canals are large and I need to have almost closed ear molds. When I first started wearing hearing aids needed much larger vents than now. So I guess what I am saying is that as our hearing changes so do our needs for aids and domes/ear molds. Your Audi should know what is best for your needs. Also now days with the modern aids, most hearing aid companies have computer modeling that determines the type of domes/ear molds, and even the needed vents and receiver power. It all comes down to the impressions, and the results of your hearing test and word understanding.