The replaceable Volume Knob only for Fosi Audio ZA3 Amplifier. To replace the knobs, Just need a cloth with friction, simply grasp the existing knob firmly and pull it straight off the shaft. Then, align the knob onto the shaft and press it firmly in place. Make sure that the knob is securely attached before use. Colour:As Shown Material:Aluminum Alloy Note: This is just a replacement knob, does not include the power amplifier. Due to different product batches, the appearance may vary, which does not affect the use Package Contents: 1 * Volume Knob Only the above package content, other products are not included. Note: Light reflection 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.