Disclosed is a disk drive apparatus including a chassis having a disk insertion slot through which a disk-type recording medium is inserted andor ejected; a disk transfer mechanism by which the disk-type recording medium is transferred between a disk ejection position and a disk loading position. The expandable bag is changeable from an unexpanded state to an expanded state by inflating the bag through the introduction of an inflation gas into the interior through the inlet part. Particles of a set size are drawn by air suction through the classifying channels in the first stage. The invention also relates to a corresponding lithium silicate glass, a process for the preparation of the glass ceramic and of the glass as well as their use.