A CD disc that is 80mm (3 1/8") in diameter. Mini CDs hold 20 minutes of CD-DA audio compared to 75 minutes for the full-size 120mm (4 3/4") disc, or 180MB of data compared to 700MB. The mini CD fits in the inner well of the CD tray or snaps onto the spindle of a laptop drive (see below).
Mini DVDs Are the Same Size
Using the same platter size as the mini CD, mini DVDs hold 1.4GB of video compared to 4.7GB for the regular 120mm DVD. See DVD
Beware Slot Loading Drives
Before inserting a mini CD or mini DVD into the slot of a "feed drive," read the manual. Many feed drives do not accept the smaller platters and can be damaged. However, the small disc can be snapped into an 80-120mm adapter and then inserted. See business card CD
and feed drive
Full and Mini
The 80mm mini discs are considerably smaller than their 120mm full-size counterpart.
How Drives Hold the Small Discs
The top example shows a laptop optical drive onto which discs both large and small are snapped down onto the spindle (notice the springs). Desktop drives (arrow at bottom) have a well in the middle of the tray for the smaller size.