This extra large Superslick bell cover is made from a high-quality double-brushed cotton cloth weave that will not scratch instrument surfaces. The extra large cover fits bells up to 20 and is perfect for tubas. The cover ties easily with the nylon drawstring cord. These covers will not impact the intonation of the instrument and have minimal-to-no resistance when playing. The non-stretchy material ensures even coverage surrounding the bell and can secure tightly around most bell sizes. Hand-wash only to clean. Superslick does not guarantee efficacy against stopping the distribution of respiratory aerosols that are released while playing wind and brass instruments. These bell covers are strictly to be used in an effort to mitigate aerosol spread.