A magnetic head actuator provided with a finely movable tracking device having a piezoelectric element is provided for easy wiring to the piezoelectric element and reducing problems such as wire breakage and continuity defects. Here, the throttle valve is made of resin material having a transmission property for a laser beam and includes a convex portion on a surface thereof irradiated by the laser beam. The mounting arrangement includes an upper member mountable to the headliner such that the upper member extends above the upper surface of the headliner and a lower member attachable to the upper member such that the lower member extends below the lower surface of the headliner. The gap between the pair of sheet members defines a spine for the hard cover product, whereby the opposing hard sheets defining a front cover and back cover that move together foldably.