Its exceptional acoustical design gives this bass trombone straight mute a smooth, distinct tone quality. It allows for a free-blowing sound throughout the instrument's natural range, encompassing even the pedal tones. The Jo-Ral 4B Bass Trombone Mute was designed for an exciting tonal quality that results in near-perfect intonation. They are made of spun aluminum, and have been tested to perform evenly in all registers. Many models are also available with brass bottoms-offering a slightly warmer, moderately dark sound, or with copper bottoms which produce an even warmer, darker, rich sound.