The ESP Custom Lab Metal Knob Noise Killer is a part that eliminates the uncomfortable shaft debris when using metal knobs. The shaft of the volume pot is structurally unstable ground ground. Therefore, the metal volume knob will make the ground falling through your fingers unstable and the shaft crunching noise. The metal knob noise killer is a special washer that has been processed into a plate spring form and is sandwiched between the pot body and the knob, thus forcing both sides to pass electricity.