5 1/4-inch floppy disk drive expansion unit.. Mates via edge connector with the related System Unit (X2408.2002A) in a piggyback arrangement.. The two pieces are mated together in storage.. The object has two 5 1/4 inch floppy disk drive bays in the front panel, but only one bay has an installed drive. The other drive bay is blocked by plastic tabs molded into the case.