JoRal TRB1 PTenor Trombone Practice Mute Jo-Ral mutes also feature neoprene-enhanced composite cork pads that provide extra durability. The result is a more pliable cork that grips well and doesn't dry out, become brittle, or break off, so it lasts longer while easily accommodating fine adjustments for a perfect fit Designed and tested to perform evenly in all registers