Item :4pcs knobs . , never used . Use for Amp Knob / Guitar Effect Pedal Knob, fit 6mm Pot. The central middle hole is approx. 6mm in diameter . White Flush Flat Knobs in Black Line. Colour:Transparent + silver Material:Acrylic + Metal Size:1.9*1.87*1.48cm Package Contents: 8 x knobs 2 x wrench Only the above package content, other products are not included. Note: Light and different displays may cause the color of the item in the picture a little different from the real thing. The measurement allowed error is +/- 1-3cm.