Whispercomforts Fv-Wc04Ve1 Polypropylene Wall Cap Accessory with Styrofoam Adaptor Conveniently Allows Both Exhaust (From the Right) and Supply (From the Left) Airflow Through a Single 5.5" -5.75" Penetration in the Building Envelope. Due to the Dividers Inside of the Unique Y-Shape Chamber and the New Wall Cap, Cross Contamination is Prevented