Using this wind instrument cover is easy. First, measure your instrument's bell size to make sure it's between 27 and 29 inches. Then, put the cover over the bell opening and use the elastic closure and cord lock to secure it in place. During use, you'll enjoy a breathable performance with little impact on acoustics. When it comes to the filter, don't wash it. Replace it every 1 - 2 months for the best results. The cover itself is reusable. You can hand - wash it to keep it clean. Keep in mind that this cover hasn't been officially tested to prevent virus transmission, so use it as an additional safety measure.