Best Brass e-Brass III practice mute for trombone, digital echo function with 3 modes, 3,5 mm input jack allows an external sound source to be combined with the signal coming from the mute or microphone, 3,5 mm Output/ phones jack allows the system to be connected to earphones for private practice, an external sound system for sound reproduction, or to a recording system for recording. 3 Choice from S to M and L with echo function, lightweight (only 110g), compact size, very silent (approx. 30dB), for trombone