This vent cover functions as a return air vent grille, designed for optimal airflow, increasing the efficiency of HVAC systems, and it helps maintain air pressure and improve air quality by filtering out debris. Suitable for residential and commercial heating, ventilation, and air conditioning systems. It is best suited for temperatures ranging from -4 °F to 176 °F. Specification: Material: ABS Plastic Inner Size: 340 x 340mm / 13.4 x 13.4 inch (L*W) Outer Size: 390 x 390 x 35mm/ 15.4 x 15.4 x 1.4 inch (L*W*H) Applicable Duct Opening Size: 350 x 350mm / 14 x 14 inch (L*W) Packing Listing: 1 x Ventilation Grille Advantage: Made of ABS plastic, smooth surface, temperature-resistant, sturdy, durable, and not easy to color-fade. It features a louver design, and with a built-in mesh screen design, it can effectively prevent dust from entering the interior and keeping it dry. The vent cover has a removable face/door, which allows you to maintain and clean easily. Instruction: 1. Attach and embed the vent cover to the ventilation duct opening. 2. Fix the vent cover to the duct opening with screws(not included). Note: 1. Please regularly clean the mesh filter of the vent grille to ensure its ventilation efficiency. 2. Please check the size carefully before purchasing. The duct opening size should be at least 5mm bigger than the inner size of the vent grille.