Oh, Oticon call these Earmolds. A DIY School PDF file named
(Fitting Instructions Oticon Genie2; More-Own)
has a link (at the very end) to; Genie 2 | 2022.1 Quick Fitting Guide.
The guide has information about Oticon Earmolds starting around pages 24/25.
Your audiologist chooses the vent size based on your hearing loss.
eta: Your (85dB earphone) is usually called a receiver or a speaker.