This set of 3 official Fender Jazz Bass Control Knobs has 2 x large knobs and 1 x small knob all with set screws to tighten onto the control potentiometer shaft and white indicator lines for easy visual adjustment. The knobs fit 1/4" (6.35 mm) imperial solid shaft potentiometers as used on most US and Mexico made Jazz Bass models manufactured from 1964 to present.