The Shugart SA-400 floppy disk drive reads and writes 35-track single-sided double-density 5.25-inch floppy disks.

In 1976, An Wang of Wang Laboratories met with Shugart Associates to ask them to produce a smaller disk drive, suitable for use with a desktop computer. At that time, the standard disk size was the 8-inch format originally developed by IBM.

In Septemer 1976, Shugart introduced the 5.25-inch flexible disk drive and diskette. Shugart called their new format the "minifloppy", trademarking the name on September 20, 1976.

Both the drives and the disks for the newer 5.25-inch disk format were less expensive than the older 8" format, and the new technology proved popular. 

The key features of the SA-400 were:

• Compact size and weight: 3.25" high x 5.75" wide x 8.0" deep, and weight of three pounds.
• 110 Kbyte (unformatted) storage capacity
• 125 Kbits / second transfer rate
• Low heat dissipation (15 watts or less)
• Positive media insertion to avoid media damage
• DC drive motor (eliminates AC requirements)
• Proprietary R / W head designed and manufactured by Shugart
• Write protect circuitry