The Phonak Brio 4 Custom is a line of custom-molded hearing aids sold exclusively through Costco Hearing Aid Centers, built on Phonak's Marvel technology platform (equivalent to the Phonak Audéo M90). Each device is individually crafted to fit the precise contours of the wearer's ear canal, offering a secure, comfortable, and discreet fit. The lineup includes multiple styles to accommodate different degrees of hearing loss and cosmetic preferences: In-The-Ear Full Shell (ITE FS), Mini Canal (MC), Completely-in-Canal (CIC), and Invisible-in-Canal (IIC), with deeper-fitting models offering greater discretion.

The Brio 4 Custom features AutoSense OS 3.0, an automatic sound environment processing system that continuously analyzes the listening environment and transitions seamlessly between programs such as speech in noise, calm situations, and music. It connects directly via Bluetooth to both iOS and Android smartphones for audio streaming and hands-free phone calls, and is controllable through the myPhonak app. Select models include a telecoil for compatibility with hearing loop systems found in theaters, churches, and public venues. The hearing aids carry an IP68 rating, meaning they are dust-tight and can withstand submersion in one meter of water for up to 60 minutes.