The replaceable volume knob is compatible with Fosi Audio V3 Amplifier. To replace the knobs, use a cloth for grip, firmly grasp the existing knob and pull it straight off the shaft. Align the new knob onto the shaft and press it firmly into place. Ensure the new knob is securely attached before use. Note: Due to different production batches, there may be slight variations in appearance, which do not affect functionality. Color: As shown Material: Aluminum alloy Package Contents: 1 x Volume knob Only the above package content is included; other items are not part of this package. Note: Light reflection and differences in display screens may cause slight color variations between the image and the actual item. Measurement error allowance is +/- 1-3 cm.