Using this Gator wind instrument cover is easy. First, measure your instrument's bell size to make sure it's between 14 and 15 inches. Then, place the cover over the bell opening and use the elastic closure and cord lock to secure it. During performances, you'll enjoy its breathable design without much back pressure or acoustic loss. When it comes to the MERV - 13 filter, don't wash it. Replace it every 1 - 2 months for the best protection. After use, if it gets dirty, you can hand - wash the cover. Just remember, these covers haven't been officially tested to prevent virus transmission, so use them as an extra precaution.