Fits Marshall Pots with 6mm Shaft Pots, these knobs do not fit "d" Shaft pots. Push on fit, no brass insert or set screw, the aluminum knobs are designed for sound equipment or rotary potentiometers, used for dirty, shabby. Due to the wide variety of pots and parts on the market, be sure to check the diameter of the pots on the booster before changing the knob for the booster. Color: Black, Silver Material: ABS, Aluminum Sheet Size: About diameter 20mm, Height 16mm, Inner Diameter 6mm Package Contents: 20 * Rotary Knobs Only the above package content, other products are not included. Note: Light shooting and different displays may cause the color of the item in the picture a little different from the real thing. The measurement error is +/- 1-3cm.