Using this wind instrument bell cover is easy. First, measure your instrument's bell to make sure it's between 6 and 7 inches. Then, simply place the cover over the bell opening and use the elastic closure and cord lock to secure it in place. During use, you can enjoy the breathable design that won't affect your performance. When it comes to the removable MERV - 13 filter, don't wash it. Replace it every 1 - 2 months for the best performance. To maintain the cover, it's reusable and can be hand - washed. Just keep in mind that these covers have not been tested by official organizations to prevent virus transmission.