The Phonak NAIDA S CRT gives the power of a big behind the ear hearing aid in a little package. A member of the receiver in the canal family, the CRT allows the wearer a variety of fitting options to grow with progressive hearing loss over time. Excellent for active lifestyles – water, sweat, moisture, and dust resistant. A better choice for a CROS fit than the Audeo S Smart series due to fact that the CRT has a 13 battery and, therefore, increased battery life. The receiver that sits in the ear canal has different power options, allowing the aid to increase in power as needed.