Ultra slim CD player. Only slightly thicker than a CD jewel case, including battery. What makes it possible is the sophisticated technology lavished on the unit, including a newly developed optical pickup (laser coupler), a thin brushless motor, highly integrated circuits, and other Sony innovations of the day. The familiar ring shape makes a reappearance on the lid of the D-J50. The ring motif had been removed from previous CD players to make room for controls, but here, all buttons are on the front. The design of the included rechargeable battery is reminiscent of slits on a CD jewel case.