This is a set of 2 metal shell dome knobs that play visuals along with the sound. Bass guitar parts for volume adjustment. Electric guitar volume control knob. Diameter: 20mm, Shaft diameter: 6mm. These metal dome knobs can be used to adjust the volume of an electric guitar or electric bass. Recommended item for guitar enthusiasts. [Product Specifications] Height: Approximately 19.7mm Diameter: Approximately 20mm Shaft diameter: Approximately 6mm The shell pattern part is a natural product, so the texture will vary for each one.