A
combo floppy drive
combines a 5 1/4" floppy drive and a 3 1/2" floppy drive
into one "disk drive unit." This drive takes up a half slot and allows you
to free up a
bay
for some other type of drive.
Although this floppy drive is not as common as its 5 1/4" and 3 1/2"
cousins, it is becoming more popular as more PC manufacturers begin to include
this drive in their systems.