The adjustable Jo-Ral B7 Bass Trombone Cup Mute is the ideal choice for deep, melodious sound. The B7 trombone mute features a neoprene rubber liner that eliminates vibrations and holds the mute firmly in place. To adjust the fit, simply move the mute up to the desired length for a tight seal and smooth cup sound, filing the corks if necessary for an even tighter fit.