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 bottoms-offering a slightly warmer moderately dark sound or with copper bottoms-which produce an even warmer darker rich sound.