Soulo Mute Adjustable Trombone Cup Mute, Soulo Adjustable Trombone Cup Mute SM7738, made of specially formulated fiber composite material much like the old Humes and Berg and Ray Robinson cups. Unlike the old school cup mutes however, which sound amazing, but struggle with the pitch, Soulo Cup is perfectly in tune in all registers. Its lightweight material allows for minimal back-pressure, weighs 6.6oz