This is the Audicus Dia II behind the ear hearing aid with open fit. It has one button with which you adjust volume programs, a battery compartment which holds your battery and turns the aid on when closed, a retention guard which curls to the shape of your ear, keeping the hearing aid in place, a silicone dome which seals to your ear canal, and amplifies the sound coming from the device into your ear, and an open tube which sends the sound to the ear.