The Jo-Ral 1C Trumpet Mute is made of aluminum with a copper bottom. The acoustical design of the Jo-Ral mutes creates the most exciting tonal quality, resulting 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 bottomsoffering a slightly warmer, moderately dark sound, or with copper bottomswhich produce an even warmer, darker rich sound.