An oblique angle was made in a corner of a rectangular parallelepiped with the curvy line of a thumb, which is the most frequently used way to control the product, completing a simple and understated body shape. The biggest strength is that the volume can be controlled simply by running a finger up and down, as the volume wheel is slightly elevated over the surface of the concave oblique angle. The details of the volume wheel, engraved with diamond knurl patterns on a simple body, increase product completion and provide the convenience to operate the product with one hand without sliding. It is easy to operate with one hand thanks to its compact size.