Using this wind instrument cover is easy. First, measure your instrument's bell size to make sure it's between 2 and 3 inches. Then, place the cover over the bell opening and use the elastic closure and cord lock to secure it. During performance, you'll enjoy clear sound as the cover has a breathable design. The removable MERV - 13 filter helps reduce aerosol spread, but don't wash it. Replace the filter every 1 - 2 months for best results. When you're done using the cover, you can hand - wash it and reuse it. Remember, this cover hasn't been tested by official organizations for preventing virus transmission.