Behind-the-Ear (BTE) hearing instruments are the largest models and can house a variety of circuit options and amplify sounds to a greater degree than most custom models. BTE's rest behind the ear and sound is sent to the ear canal via the earmold and clear plastic tubing molded to fit comfortably in the outer ear area.

In-the-Ear (ITE) instruments house a variety of circuit options in a custom-made shell designed to fit in the outer portion of the ear. Its size and easy-to-use controls may also be helpful for people with limited dexterity.

In-the-Canal (ITC) instruments are custom designed to fit in the ear canal. ITCs are discreet, yet still slightly visible within the outer ear. ITC instruments offer a variety of circuit choices that would have previously required a larger aid.

Completely-in-the-Canal (CIC) instruments are the smallest and most discreet aids available. CICs are custom designed to fit entirely in the ear canal, improving sound quality and reducing feedback. CICs are popular for their aesthetic appeal, but the physiology of some individuals' ears may make the style unsuitable for them.