The powerful Serene CL-Link Tele-Coil Coupler diminishes outside noise and was designed to work with your Serene amplified telephone and all phones equipped with a 2.5mm or 3.5mm output jack. Built-in microphone. Lightweight silicone padding makes this telephone accessory comfortable to wear. For t-coil hearing aid wearers. Due to health and sanitary reasons, this item is non-returnable.