Guitar AMP Knobs Top Fits Marshall Amplifier, 20 Pcs Black with Gold Top Brand new, never used.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.