Guitar AMP Knobs Top Fits Marshall Amplifier, 20 Pcs Black with Silver Cap Brand new, never used.Color: Black with Silver Cap Material: Please note the knobs including Cap are all made of ABS/Plastic, not Metal or Aluminum. Total Length: about 15.5 mm.Outer diameter at the top: about 15.6 mm.Outer diameter at the base: about 20 mm. These are Push on fit knobs, without set screw.Fit for MARSHALL Amplifers with 6.4 mm diameter pots. Package Includes: 20pcs AMP Knobs.