Play with rich, big open cup mute tones. Free easy-blowing in all registers. Excellent intonation for solo or section work. You'll experience a command performance. Willie Berg invented Stone lined Mutes in 1935. They are the finest Brass Instrument Mutes available in the World. Stone lined Mutes play perfectly in tune and are easy blowing. For the perfect professional sound all the time, our line of Stone lined Mutes offers many different models to produce outstanding various tonal colors for the Brass player.