Guitar AMP Knobs Top Fits Marshall Amplifiers, 20 Pcs Black/gold 20 Guitar AMP Knobs Color: Black with Gold Top Material: Please note the knobs including Cap are all made of ABS/Plastic, not Metal or Aluminum Total Length: about 15.5mm. Outer diameter at the top: about 15.6mm. Outer diameter at the base: about 20mm. These are Push on fit knobs, without set screw. Fit for MARSHALL Amplifers with 6.4mm diameter pots. Package Includes: 20pcs AMP Knobs