2 kinds of Volumes adjustment. is to increase the adjustment to make the song sound louder, and the other is to reduce the Volumes. Very comfortable and easy to adjust. Good material The controller is made from and plastic. The has good electrical conductivity for optimal mission. The controller is easy to install without wiring. Simple installation, can be directly adjusted when installed. More convenient to adjust the Volumes of the Volumes. Specifications: Connector:4-core Note: The cable interface is a 4-core crystal head, which is not suitable for the power amplifier of 6 stitches Colour:black Material:Plastic The actual product may have slight color difference or difference, which not affect the use Package Contents: 1 x Amplifier Bass 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.