The wind instrument double-layer bell cover for 11 to 13-inch French Horn bell sizes fits securely over the bell opening of your instrument to help reduce the spread of aerosols during use. The cover comes equipped with a hand access slot for proper horn grip and is designed to meet the recommendations set forth by the Performing Arts Aerosol Study commissioned by the National Federation of State High School Association (NFHS). An elastic closure lets you stretch and place the cover directly over the instrument's bell opening to ensure proper fitment. To clean, simply hand wash and let air dry (do not machine wash). To guarantee best fitment, be sure to measure the bell diameter of your instrument prior to ordering. Disclaimer: These masks have not been tested by the FDA, CDC or any other official organization to conclude that they prevent the transmission of viruses.