Hearing aid which fits in the canal of the outer ear. An in-the-canal (ITC) hearing aid fills the outer part of the ear canal and a small part of the concha bowl of the outer ear. ITC hearing aids are most appropriate for mild to moderately-severe hearing loss. They include a microphone, amplifier, digital processor, receiver, and battery. ITC hearing aids fit best when they are custom made using an ear impression of the ear canal. It is a type of custom hearing aid.