Cut to Any Size: 12" x 5.5" magnetic vent cover fits most standard air registers and can be freely cut to fit specific vents. Good Flexibility: Excellent flexibility ensures it contours around floor vents to completely eliminate airflow. The magnetic side of this product only works with steel materials, it will not work with aluminum, plastic, or wood. Please test with a magnet before application. Double Thickness: Made of double-thickness magnetic material, the cover can grip your vent securely in place. The magnetic vent cover sticks firmly to floor/ceiling/wall vents, will not slide. Can be used for homes, RVs, HAVC units, and furnace vents. Energy Saving: These covers allow you to efficiently distribute your airflow or close registers in spaces that are not fully utilized. Reduce your energy costs by not heating or cooling unused spaces. Redirect airflow to the areas needed for better comfort. Note: The data are all manually measured, please allow an error of 1-3 cm. Due to differences in light and display, there may be color differences, please refer to the actual item received.